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{{Short description|Signaling device to control competing flows of traffic}} | |||
{{mergefrom|Red light running|discuss=Talk:Red light running#Proposed merge with Traffic light#Legal implications|date=July 2015}} | |||
{{about|lights used for signalling}} | |||
{{use dmy dates|date=October 2012}} | |||
{{redirect|Stoplight}} | |||
{{multiple issues| | |||
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{{Use dmy dates|date=February 2024}} | ||
] traffic light in ], United Kingdom]] | |||
{{more footnotes|date=October 2013}} | |||
'''Traffic lights''', '''traffic signals''', or '''stoplights''' – also known as '''robots''' in ],<ref>{{cite web|url=https://en.oxforddictionaries.com/definition/robot|archive-url=https://web.archive.org/web/20180814235213/https://en.oxforddictionaries.com/definition/robot|url-status=dead|archive-date=14 August 2018|title=robot – definition of robot in English – Oxford Dictionaries|website=Oxford Dictionaries – English}}</ref><ref>{{cite web |title=see robot – definition of robot in Dictionary of South African English. |url=https://dsae.co.za/entry/robot/e06032 |website=Editor's Note: The origin of 'robot' used as 'traffic light' is from the English translation of the play ] by ] which debuted in England in 1923 which introduced the term 'robot' to an English audience. For a short time in England it was fashionable to use 'robot' for 'traffic light' from the late 1920s, when traffic lights were being installed in England. This usage travelled to South Africa in the early 1930s, when they had their first traffic lights installed, and where it continues to be used almost 90 years later, while 'robot' for 'traffic light' fell out of usage in England. See Foster, B. 1970. The changing English language. Harmondsworth, Middlesex: Penguin.}}</ref> ], and ] – are signaling devices positioned at ], ]s, and other locations in order to control the flow of traffic.<ref>{{cite journal |last1=McShane |first1=Clay |title=The Origins and Globalization of Traffic Control Signals |journal=Journal of Urban History |date=March 1999 |volume=25 |issue=3 |pages=379–404 |url=https://sites.tufts.edu/carscultureplace2010/files/2010/09/McShane-traffic-signals-1999.pdf |access-date=27 October 2019 |doi=10.1177/009614429902500304 |s2cid=110125733}}</ref> | |||
}} | |||
], England]] | |||
]s in ]]] | |||
'''Traffic lights,''' also known as '''traffic signals, traffic lamps,''' '''traffic semaphore''', '''signal lights''', '''stop lights''' and '''robots''',<ref>. Mydriverslicence.co.za.</ref> and also known technically as '''traffic control signals'''<ref> The Origins and Globalization of Traffic Control Signals — Retrieved 08 December 2013</ref> are signalling devices positioned at ], ]s and other locations to control conflicting flows of traffic. The first manually operated gas-lit traffic light was installed in 1868 in ], though it was short-lived due to explosion. The first safe, automatic electric traffic lights were installed in the ] starting in the late 1890s.<ref>. (PDF)</ref> | |||
Traffic lights normally consist of three signals, transmitting meaningful information to road users through colours and symbols, including arrows and bicycles. The regular traffic light colours are ] to stop traffic, ] for traffic change, and ] for allowing the traffic, arranged vertically or horizontally in that order. Although this is internationally standardised,<ref name=":5">{{cite book | publisher=United Nations. Economic Commission for Europe. Transport Division | title=Convention on Road Signs and Signals of 1968; European Agreement Supplementing the Convention; and, Protocol on Road Markings, Additional to the European Agreement : (2006 consolidated versions) | url = https://unece.org/transport/publications/convention-road-signs-and-signals-1968-european-agreement-supplementing | publication-place=New York | date=2007 | isbn=978-92-1-139128-2 | oclc=227191711}}</ref> variations in traffic light sequences and laws exist on national and local scales.<ref>see ]</ref> | |||
Traffic lights alternate the ] accorded to road users by displaying lights of a standard color (red, yellow, and green) following a universal ]. In the typical sequence of color phases: | |||
* the green light allows traffic to proceed in the direction denoted, if it is safe to do so | |||
* the yellow (or amber) light warns that the signal will be changing from green to red (and from red to green in certain countries, such as in the UK<ref>{{cite web|url=http://www.drivingtesttips.biz/traffic-lights-sequence.html|title=Traffic Lights Sequence|work=drivingtesttips.biz}}</ref>). Actions required by drivers on an amber light vary, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so. | |||
* a flashing yellow indication is a warning signal | |||
* the red signal prohibits any traffic from proceeding | |||
* a flashing red indication is treated as a ] | |||
Traffic lights were first introduced in December 1868 on ] in ] to reduce the need for police officers to control traffic.<ref name=":7">{{Cite web |last=Thames Leisure |title=12 Amazing Facts About London |url=http://www.thamesleisure.co.uk/12-amazing-facts-london/ |url-status=dead |archive-url=https://web.archive.org/web/20170107005431/http://www.thamesleisure.co.uk/12-amazing-facts-london/ |archive-date=7 January 2017 |access-date=25 January 2017}}</ref> Since then, electricity and computerised control have advanced traffic light technology and increased intersection capacity.{{sfnp|Sessions|1971|p=141}} The system is also used for other purposes, including the control of pedestrian movements, variable lane control (such as ] systems or ]s), and railway ]s. | |||
In some countries traffic signals will go into a flashing mode if the controller detects a problem, such as a program that tries to display green lights to conflicting traffic. The signal may display flashing yellow to the main road and flashing red to the side road, or flashing red in all directions. Flashing operation can also be used during times of day when traffic is light, such as late at night.<ref>{{cite news|url=http://whatisusa.info/driving-in-america/|title=driving in America|publisher=What is USA News|date=10 March 2014 | accessdate=2013-09-16}}</ref> | |||
== History == | == History == | ||
{{Main|History of traffic lights}} | |||
] in December 1940]] | |||
The first system of traffic signals, which was a semaphore traffic signal, was installed as a way to replace police officer control of vehicular traffic outside the ] in ] on 9 December 1868. This system exploded on 2 January 1869 and was thus taken down. But this early traffic signal led to other parts of the world implementing similar traffic signal systems. In the first two decades of the 20th century, ] traffic signals like the one in London were in use all over the ]. These traffic signals were controlled by a ] who would change the commands on the signal to direct traffic.{{sfnp|Sessions|1971|p=22}} | |||
] traffic signal. Formerly fitted in various intersections in ], Australia, indicating how much time remained before a signal change.]] | |||
On 9 December 1868,<ref>City of Westminster ] on the site</ref> the first, non-electric, gas-lit traffic lights were installed outside the ] in ] to control the traffic in Bridge Street, Great George Street and Parliament Street. They were promoted by the railway engineer ] and constructed by the railway signal engineers of ] & Farmer. The design combined three ] arms with red and green gas lamps for night-time use, on a pillar, operated by a ]. The gas lantern was manually turned by a traffic police officer, with a lever at its base so that the appropriate light faced traffic.<ref>{{cite web|author=University of London|url=http://www.victoriacountyhistory.ac.uk/explore/items/westminster-road-semaphore |title=Westminster Road Semaphore|publisher=Victoria County History |accessdate=2013-02-03}}</ref> | |||
In 1912, the first electric traffic light was developed by ], a policeman in ], ].<ref>{{cite web |last=Bellis |first=Mary |date=5 February 1952 |title=The History of Roads and Asphalt |url=http://theinventors.org/library/inventors/blasphalt.htm |website=theinventors.org }}</ref> It was installed by the American Traffic Signal Company on the corner of East 105th Street and ] in ], Ohio, on August 5, 1914.{{sfnp|Sessions|1971|pp=27–28}}<ref>{{cite journal |date=August 1914 |title=New Traffic Signal Installed |journal=The Motorist |publisher=Ken Pub. Co |pages=28–29}}</ref><ref>{{Cite web |title=Traffic signals: A brief history |website=Washington State Magazine |publisher=Washington State University |first1=Larry |last1=Clark |date=Fall 2019 |url=https://magazine.wsu.edu/web-extra/traffic-signals-a-brief-history/ |access-date=19 December 2021 |language=en-US}}</ref> The first four-way, three-colour traffic light was created by ] in ] in 1920.<ref name=":11" /> His design was the first to include an amber 'caution' light along with red and green lights.<ref name=":12" /> Potts was Superintendent of Signals for the Police Department of Detroit. He installed automatic four-way, three-colour traffic lights in 15 towers across Detroit in 1921.<ref name="Pollard082">{{cite journal |last=Pollard |first=Justin |date=September 2008 |doi-access=free |url=https://digital-library.theiet.org/content/journals/10.1049/et_20081518 |via=IET Digital Library |title=The Eccentric Engineer: The History of Traffic Lights Is Full of Twists and Turns |journal=Engineering and Technology |volume=3 |issue=15 |page=93 |doi=10.1049/et:20081518 |doi-broken-date=7 December 2024 }}</ref><ref name=":12">{{cite web |url=https://www.thehenryford.org/collections-and-research/digital-collections/artifact/227457/#slide=gs-225140 |title=First Tri-Color, Four-Directional Traffic Signal, 1920 |website=The Henry Ford |url-status=live |archive-url=https://web.archive.org/web/20240312133450/https://www.thehenryford.org/collections-and-research/digital-collections/artifact/227457/#slide=gs-225140 |archive-date= Mar 12, 2024 }}</ref><ref name=":11">{{cite web |url=http://large.stanford.edu/courses/2011/ph240/miller1/docs/moyer/ |title=Mr. 'Trafficlight' |date=March 1947 |first1=Sheldon |last1=Moyer |work=Motor News |via=large.stanford.edu |url-status=live |archive-url=https://web.archive.org/web/20230913014058/http://large.stanford.edu/courses/2011/ph240/miller1/docs/moyer/ |archive-date= Sep 13, 2023 }}</ref> By 1922, traffic towers were beginning to be controlled by automatic timers more widely. The main advantage of the use of the timer was that it saved cities money by replacing traffic officers. The city of ] was able to reassign all but 500 of its 6,000 officers working on the traffic squad, saving the city $12,500,000.{{sfnp|McShane|1999|p=385}} | |||
Although it was said to be successful at controlling traffic | |||
its operational life was brief. It exploded on 2 January 1869, as a result of a leak in one of the gas lines underneath the pavement, injuring<ref>{{cite news| url=http://www.bbc.co.uk/nottingham/content/articles/2009/07/16/john_peake_knight_traffic_lights_feature.shtml| title=The man who gave us traffic lights| date=22 July 2009| publisher=BBC | accessdate=2009-11-08}}</ref> or killing<ref>{{cite book|last=Day|first=Lance|author2=Ian McNeil |title=Biographical dictionary of the history of technology|publisher=Taylor & Francis|year=1996|pages=404–5|isbn=0-415-06042-7|url=http://books.google.com/?id=9HQDGHQzVqAC&pg=PA404&lpg=PA404&dq=John+Peake+Knight%2Bobituary&q=John%20Peake%20Knight%2Bobituary}}</ref> the policeman who was operating it. With doubts about its safety, the concept was abandoned until electric signals became available. | |||
In 1923, ] patented a design of a manually operated three-way traffic light with moving arms.<ref>{{cite web |url=https://patents.google.com/patent/US1475024A/en |title=US Patent: US1475024A 'Traffic signal' (1923) |website=patents.google}}</ref> | |||
The first electric traffic light was developed in 1912 by ], a policeman in ], ], who also used red-green lights.<ref>{{cite web|author=Mary Bellis |url=http://inventors.about.com/library/inventors/blasphalt.htm |title=The History of Roads and Asphalt |publisher=Inventors.about.com |date=5 February 1952 |accessdate=2009-05-19}}</ref> On 5 August 1914, the ] installed a traffic signal system on the corner of East 105th Street and ] in ], ].<ref>{{cite book|last=Sessions|first=Gordon M.|title=Traffic devices: historical aspects thereof|year=1971|publisher=Institute of Traffic Engineers|location=Washington|oclc=278619|pages=27–28}}</ref><ref>{{cite journal|title=New Traffic Signal Installed|journal=The Motorist |publisher=Ken Pub. Co|pages=28–29|date=August 1914}}</ref> It had two colors, red and green, and a ], based on the design of James Hoge, to provide a warning for color changes. The design by James Hoge<ref>{{cite web|url=http://patimg2.uspto.gov/.piw?Docid=01251666&PageNum=6&idkey=NONE |title=USPTO # 1251666 Sept. 22, 1913 |publisher=Patimg2.uspto.gov |accessdate=2009-05-19}}</ref> allowed police and fire stations to ]. The first four-way, three-color traffic light was created by police officer ] in ], ] in 1920.<ref>{{cite journal|first=Sheldon|last=Moyer|title=Mr. 'Trafficlight'|journal=Motor News|publisher=Automobile Club of Michigan|pages=14–15, 27|date=March 1947| url=http://www33.brinkster.com/iiiii/trfclt/mrtrafficlight/mrtrafficlight.html}}</ref> ], Ohio claims to be the home of the oldest working traffic light in the United States, used at an intersection of public roads from 1932 to 1982 when it was moved to a local museum.<ref>. ''Ashville Area Heritage Society''. Retrieved 2008-04-16.</ref><ref>. ''RoadsideAmerica.com''. Retrieved 2014-02-11.</ref> | |||
The control of traffic lights made a big turn with the rise of ] in America in the 1950s. One of the best historical examples of computerized control of lights was in ] in 1952. In 1967, the city of ] was the first to use more advanced computers that were better at vehicle detection.{{sfnp|Sessions|1971|p=141}} The computers maintained control over 159 signals in the cities through telephone lines.{{sfnp|Sessions|1971|p=143}} | |||
Los Angeles installed its first automated traffic signals in October 1920 at five locations on Broadway. These early signals, manufactured by the Acme Traffic Signal Co., paired “Stop” and “Go” semaphore arms with small red and green lights. Bells played the role of today's amber or yellow lights, ringing when the flags changed—a process that took five seconds. By 1923 the city had installed 31 Acme traffic control devices.<ref>. ''Los Angeles Magazine''. Retrieved 2015-01-01.</ref> The Acme semaphore traffic lights were often used in ] ] and ] cartoons for comedic effect due to their loud bell. | |||
==Vehicular signals== | |||
The first interconnected traffic signal system was installed in ] in 1917, with six connected intersections controlled simultaneously from a manual switch.<ref>{{cite book|last=Sessions|first=Gordon M.|title=Traffic devices: historical aspects thereof|year=1971|publisher=Institute of Traffic Engineers|location=Washington|oclc=278619|page=32}}</ref> Automatic control of interconnected traffic lights was introduced March 1922 in ], ].<ref>Section 1.5: "System Evolution", '''', ] Report FHWA-HOP-06-006, October 2005.</ref> The first traffic lights in England were deployed in ] in 1926.<ref>{{cite web|title=Traffic Controls|url=http://www.museumoflondon.org.uk/Collections-Research/Research/Your-Research/X20L/Themes/1/1240/|work=Exploring 20th Century London|publisher=The Museum of London|accessdate=24 June 2013}}</ref> | |||
] | |||
] with ]'s runway in ]. The movable barrier closes when aircraft land or take off.]] ]A set of lights, known as a signal head,<ref name=":1">. ''Department for Transport, Department for Infrastructure (Northern Ireland), Transport Scotland and Welsh Government''. Accessed: 18 December 2021.</ref>{{Rp|location=3.2.4}} may have one, two, three, or more aspects. The most common signal type has three aspects facing the oncoming traffic: red on top, amber (yellow) below, and green below that. Additional aspects may be fitted to the signal, usually to indicate specific restrictions or filter movements. | |||
Wolverhampton was the first town in Britain to introduce automated traffic lights in 1927 in Princes Square at the junction of Lichfield Street and Princess Street. | |||
=== Meanings of signals === | |||
] was the first city in ] to install traffic lights in 1928 on the intersection of Collins and Swanston Street. | |||
The ] Chapter III provides international standards for the setup of traffic signal operations. Not all states have ratified the convention. A three-colour signal head should have three non-flashing lights which are red, ], and green, either arranged horizontally (on the side opposite to the direction of traffic) or vertically (with red on top). A two-colour signal head may be used in temporary operation and consists of red and green non-flashing lights. In both cases, all lights should be circular or arrow-shaped.<ref name=":5" /> Permissible signals for regulating vehicle traffic (other than public transport vehicles) are outlined in Article 23:<ref name=":5" /> | |||
{| class="wikitable" | |||
|+Standard meanings for traffic lights internationally (Vienna Convention, Article 23) | |||
! colspan="2" |Light type | |||
!Meaning | |||
|- | |||
| rowspan="4" |Non-flashing | |||
|Red | |||
|Traffic may not proceed beyond the stop line, or otherwise enter the intersection | |||
|- | |||
|Red/Amber | |||
|The signal is about to change, but the red light rules do apply | |||
|- | |||
|] | |||
|Traffic may not pass the stop line or enter the intersection, unless it cannot safely stop when the light shows | |||
|- | |||
|Green | |||
|Traffic may proceed, unless it would not clear the intersection before the next change of phase | |||
|- | |||
| rowspan="2" |Flashing | |||
|Red | |||
|Traffic must not pass the stop line at a level crossing, approach to swing bridge or ferry landing stages, emergency vehicles entering the road, or on the approach to low-flying aircraft. In addition, to attract attention in these locations, it is also equipped with additional alarms and voice prompts | |||
|- | |||
|Amber | |||
|Traffic may proceed with caution | |||
|} | |||
Green arrows are added to signals to indicate that drivers can travel in a particular direction, while the main lights for that approach are red, or that drivers can only travel in one particular direction. Alternatively, when combined with another green signal, they may indicate that turning traffic has priority over oncoming traffic (known as a "filter arrow").<ref name=":1" />{{Rp|location=3.5}} Flashing amber arrows typically indicate that road users must give way (to other drivers and pedestrians) before making a movement in the direction of the arrow. These are used because they are safer, cause less delay, and are more flexible. Flashing amber arrows will normally be located below the solid amber.<ref>{{Cite web |title=Flashing Yellow Arrow Traffic Signals – Traffic Engineering – MnDOT |url=https://www.dot.state.mn.us/trafficeng/signals/flashingyellowarrow.html |access-date=18 December 2021 |website=www.dot.state.mn.us}}</ref> | |||
==== Green arrows ==== | |||
], ] was the first city to computerize its entire traffic signal system, which it accomplished in 1963.{{citation needed|date=June 2012}} | |||
Arrow aspects may be used to permit certain movements or convey other messages to road users. A green arrow may display to require drivers to turn in a particular direction only or to allow drivers to continue in a particular direction when the signal is red.<ref name=":1" />{{Rp|location=3.5}} Generally, a green phase is illuminated at the beginning of the green phase (a "leading turn") or at the end of the green phase (a "lagging turn").{{Citation needed|date=December 2021}} An 'indicative arrow' may be displayed alongside a green light. This indicates to drivers that oncoming traffic is stopped, such that they do not need to give way to that traffic when turning across it. As right-turning traffic (left-side drive) or left-turning traffic (right-side drive) does not normally have priority, this arrow is used to allow turning traffic to clear before the next phase begins.<ref name=":1" />{{Rp|location=3.5}} | |||
Some variations exist on this set up. One version is a horizontal bar with five lights – the green and amber arrows are located between the standard green and amber lights. A vertical five-light bar holds the arrows underneath the standard green light (in this arrangement, the amber arrow is sometimes omitted, leaving only the green arrow below the steady green light, or possibly an ]-based device capable of showing both green and amber arrows within a single lamp housing).<ref>{{Cite web |title=MUTCD 11th Edition - Part 4 |url=https://mutcd.fhwa.dot.gov/pdfs/11th_Edition/part4.pdf |access-date=13 December 2024 |website=]}}</ref> | |||
]s on traffic lights were introduced in the 1990s. Timers are useful for pedestrians, to plan whether there is enough time to cross the intersection before the end of the walk phase, and for drivers, to know the amount of time before the light turns green. In the United States, timers for vehicle traffic are prohibited, but pedestrian timers are now required on new or upgraded signals on wider roadways. | |||
A third type is known as a "doghouse" or "cluster head" – a vertical column with the two normal lights is on the right side of the signal, a vertical column with the two arrows is located on the left, and the normal red signal is in the middle above the two columns. Cluster signals in Australia and ] use six signals, the sixth being a red arrow that can operate separately from the standard red light.{{Citation needed|date=December 2021}} In a fourth type, sometimes seen at intersections in ] and ], Canada, there is no dedicated left-turn lamp per se. Instead, the normal green lamp flashes rapidly, indicating permission to go straight as well as make a left turn in front of opposing traffic, which is being held by a steady red lamp. (This "advance green", or flashing green can be somewhat startling and confusing to drivers not familiar with this system. This also can cause confusion amongst visitors to British Columbia, where a flashing green signal denotes a pedestrian-controlled crosswalk. For this reason, Ontario is phasing out the use of flashing green signals and instead replacing them with arrows.)<ref>{{cite web |title=RoadSense for Drivers – Signs, Signals and Road Markings |url=http://www.icbc.com/driver-licensing/Getting-licensed/drivers3.pdf |url-status=dead |archive-url=https://web.archive.org/web/20131022032056/http://www.icbc.com/driver-licensing/Getting-licensed/drivers3.pdf |archive-date=22 October 2013}} Accessed: 25 March 2014</ref><ref>{{Cite book |title=Ontario Traffic Manual Book 12: Traffic Signals. |publisher=Ministry of Transportation of Ontario |year=2012 |pages=55}}</ref> | |||
== Types and placement of colors== | |||
{{Main|List of variations in traffic light signalling and operation}} | |||
==== Countdown lights ==== | |||
], United Kingdom, also shows the red + yellow combination seen in a number of European countries, and a backing board with white border to increase the target value of the signal head. Improved visibility of the signal head is achieved during the night by using the retro-reflective white border.]] | |||
Popular in Vietnam and China, countdown lights are additional lights installed next to (or above or below) the main signal lights. The countdown light is displayed by a countdown number with different colors (usually red, yellow, green), matching the color of the light on. When the light counts to "0" (or 1), the main light color immediately changes. Countdown lights may have zeros in the tens or none, some countdown lights may flash when getting ready to zero. Yellow lights can also have countdown lights, but most lights do not. Usually the countdown light has 2 digits, in case the time of the main light (usually the red light, rarely the green light) is longer than 100 seconds, depending on the type of light, the following possibilities may occur: | |||
# Lights have not counted down, when 99 seconds are left, start counting. During the standby time, the light may be displayed as "99", "00", "--" or not displayed. | |||
Aspect is a term referring to the light that faces the drivers. A typical vertical traffic signal has three aspects, or lights, facing the oncoming traffic, red on top, yellow (amber) below, and green below that. Generally one aspect is illuminated at a time. In some cases, a fourth aspect, for a turn arrow for example, is below the three lights or aspects in more complicated road traffic intersections. | |||
# Last 2 digits count light of the timeout (the counter light is 15 while the time is 115 seconds, there are some types of lights that count as "-9" or "9-" when the time is 109 seconds) | |||
# Tens digit on the displayer becomes a letter. Displaying A0 for 100 seconds, B0 for 110 seconds, so forth. | |||
# Displaying only last 2 digits but with flashing to indicate it's more than 100. | |||
] | |||
==== Issue about yellow light dilemma zone in South Korea ==== | |||
=== Single aspects === | |||
In South Korea, the yellow light dilemma zone is not legally recognized. In other words, when the yellow light is on, traffic may not pass the stop line or enter the intersection even if cannot safely stop when the light shows. | |||
{{Expand section|date=March 2010}} | |||
This has been reaffirmed by the ruling of the ] in May 2024,<ref>{{cite web|title=Supreme Court rules that driver should stop when yellow light turns on even if car is expected to stop in intersection|url=https://english.khan.co.kr/khan_art_view.html?artid=202405141817347&code=710100|editor=The Kyunghyang Shinmun|date=2024-05-14}}</ref><ref>{{cite web|language=ko|script-title=ko:'갈까 말까' 딜레마존…"안 겪어보면 몰라" 판결에 분통 |url=https://news.sbs.co.kr/news/endPage.do?news_id=N1007656713|editor=SBS|date=2024-05-22}}</ref> for a case where the driver was speeding at 62 km/h in a street limited up to 40 km/h ({{#expr: ((62/40)-1)*100 round 0}} % upper than the allowed speed).<ref>{{Cite web |date=2024-05-13 |title=The Supreme Court ruled that if a yellow light is turned on at the traffic light just before enterin.. - MK |url=https://www.mk.co.kr/en/society/11014731 |access-date=2024-10-11 |website=] |language=en}}</ref>{{Unreliable source?|reason=The English version of this website uses automatic machine translation; see ]|date=November 2024}} | |||
The simplest traffic light comprises either a single or a pair of colored aspects that warns any user of the shared right of way of a possible conflict or danger. | |||
Criticism in South Korea says that this is unrealistic and unreasonable. In addition, this can cause multiple collisions due to sudden braking. | |||
In 2016 when speed limit was up to 60 km/h, proposed alternatives to this kind of collision were only roundabouts, speed compliance increase and speed practice reduction or elderly zones are also proposed solutions.<ref>https://www.itf-oecd.org/sites/default/files/docs/halving-road-deaths-korea.pdf</ref> | |||
=== Yellow trap === | |||
Without an all-red phase, cross-turning traffic may be caught in a ]. When the signal turns yellow, a turning driver may assume oncoming traffic will stop and a crash may result. For this reason, the US bans sequences that may cause a yellow trap.<ref>{{Cite web |title=Frequently Asked Questions – Part 4 Highway Traffic Signals – FHWA MUTCD |url=https://mutcd.fhwa.dot.gov/knowledge/faqs/faq_part4.htm#tcsfq3 |access-date=18 December 2021 |website=]}}</ref> This can also happen when emergency vehicles or railroads preempt normal signal operation. | |||
<ref>{{cite web |date=7 January 2015 |title=The Flashing Yellow Arrow and the Yellow Trap |url=https://streets.mn/2015/01/07/the-flashing-yellow-arrow-and-the-yellow-trap/ |access-date=3 April 2019}}</ref> In the United States, signs reading "Oncoming traffic has extended green" or "Oncoming traffic may have extended green" must be posted at intersections where the "yellow trap" condition exists.<ref>{{cite web |title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4D |url=https://mutcd.fhwa.dot.gov/htm/2003r1r2/part4/part4d.htm#section4D05 |access-date=19 May 2009 |publisher=]}}</ref><ref>{{cite web |title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 2C |url=https://mutcd.fhwa.dot.gov/htm/2003r1r2/part2/part2c.htm#section2C39 |access-date=19 May 2009 |publisher=]}}</ref> | |||
===Variations=== | |||
{{Main|Variations in traffic light operation}}The United States is not party to the ]; rather, the ] (MUTCD) outlines correct operation in that country. In the US, a single signal head may have three, four, or five aspects (though a single aspect green arrow may be displayed to indicate a continuous movement). The signals must be arranged red, amber, and green vertically (top to bottom) or horizontally (left to right).<ref name=":6">2009. . US Federal Highway Administration. URL Accessed: 7 January 2022.</ref> In the US, a single-aspect flashing amber signal can be used to raise attention to a warning sign and a single-aspect flashing red signal can be used to raise attention to a "stop", "do not enter", or "wrong way" sign.<ref name=":6" /> Flashing red or amber lights, known as ''intersection control beacons'', are used to reinforce stop signs at intersections.<ref>{{cite book |title=Manual on Uniform Traffic Control Devices |title-link=Manual on Uniform Traffic Control Devices |date=2009 |publisher=Federal Highway Administration |chapter=Section 4L.02 Intersection Control Beacon |chapter-url=https://mutcd.fhwa.dot.gov/htm/2009/part4/part4l.htm#section4L02}}</ref> The MUTCD specifies the following vehicular signals:<ref name=":6" /> | |||
{| class="wikitable mw-collapsible mw-collapsed" | |||
|+Standard meanings for traffic lights in the United States (MUTCD, Chapter 4) | |||
!Signal | |||
!Meaning (steady) | |||
!Meaning (flashing) | |||
|- | |||
!]<br />Circular green | |||
|Traffic can proceed in any permitted direction, yielding to pedestrians in a crosswalk or other vehicles when turning | |||
| rowspan="2" |Not to be used | |||
|- | |||
!]<br />Green arrow | |||
|Traffic can proceed in the direction shown by the arrow, yielding to any pedestrians in a crosswalk or other vehicles in the intersection | |||
|- | |||
!]<br />Circular yellow | |||
|The green movement is being terminated and a red signal will soon be displayed | |||
|Traffic can cautiously enter the intersection, yielding to pedestrians and other vehicles | |||
|- | |||
!]<br />Yellow arrow | |||
|The green or flashing arrow movement is being terminated | |||
|Traffic can cautiously enter the intersection to make the movement displayed by the arrow, yielding to pedestrians and other vehicles | |||
|- | |||
!]<br />Circular red | |||
|Unless another signal permits, traffic shall not enter the intersection except to lawfully ] | |||
|Traffic must stop before entering the intersection, but may then treat the signal by the same rules as a STOP sign. | |||
|- | |||
!]<br />Red arrow | |||
|Traffic shall not make the movement displayed by the arrow | |||
|Traffic must stop before entering the intersection, but may then treat the signal by the same rules as a stop sign to make the movement displayed by the arrow. | |||
|}], ], with specially shaped lights to assist people with colour blindness]] | |||
In the Canadian province of ] and the Maritime provinces, lights are often arranged horizontally, but each aspect is a different shape: red is a square (larger than the normal circle) and usually in pairs at either end of the fixture, amber is a diamond, and green is a circle. In many southern and southwestern U.S. states, most traffic signals are similarly horizontal in order to ease wind resistance during storms and hurricanes.<ref>{{cite web|title=Traffic Signals|url=http://cityofcarrollton.com/index.aspx?page=259|archive-url=https://web.archive.org/web/20100113150357/http://cityofcarrollton.com/index.aspx?page=259|url-status=dead|archive-date=13 January 2010|website=Carrollton Texas|access-date=12 July 2014}}</ref> Japanese traffic signals mostly follow the same rule except that the green "go" signals are referred to as 青 (ao), typically translated as "blue", reflecting ]. As a result, Japanese officials decreed in 1973 that the "go" light should be changed to the bluest possible shade of green, bringing the name more in line with the color without violating the international "green means go" rule.<ref>{{cite news|url=http://www.japantimes.co.jp/life/2013/02/25/language/the-japanese-traffic-light-blues-stop-on-red-go-on-what/#.WRmAuuWGNPZ|title=The Japanese traffic light blues: Stop on red, go on what|first=Peter|last=Backhaus|date=25 February 2013|work=The Japan Times|access-date=14 July 2017}}</ref> | |||
In the UK, normal traffic lights follow this sequence:<ref>{{cite web|url=http://www.legislation.gov.uk/uksi/2016/362/schedule/14/made|title=The Traffic Signs Regulations and General Directions 2016|date=2016|publisher=The National Archives|website=legislation.gov.uk|access-date=14 July 2017}}</ref> | |||
* Red – Stop, do not proceed | |||
* Red and Amber – Get ready to proceed, but do not proceed yet | |||
* Green – Proceed if the intersection or crossing is clear; vehicles are not allowed to block the intersection or crossing | |||
* Amber – Stop, unless it is unsafe to do so | |||
A speed sign is a special traffic light, variable ], or ] giving drivers a recommended speed to approach the next traffic light in its green phase<ref>{{Cite book|author=Forschungsgesellschaft für Straßen- und Verkehrswesen|title=Begriffsbestimmungen, Teil: Verkehrsplanung, Straßenentwurf und Straßenbetrieb|publisher=FGSV Verlag|year=2000|pages=81}}</ref> and avoid a stop due to reaching the intersection when lights are red.<ref>{{Cite book|author=Andreas Richter|title=Geschwindigkeitsvorgabe an Lichtsignalanlagen|publisher=DUV|year=2005|isbn=3-8244-0828-7|pages=33–34}}</ref>{{efn|Not completely correct: a variable speed sign is not solely used for the purpose of slowing the speed of motorists approaching an intersection. They are also used on freeways where the maximum safe speed is dependent on the conditions of the roadway (i.e. weather, falling rocks, risk of wildlife, etc.), such as in British Columbia, Canada.{{Clarify|reason=See note|date=July 2020}}}} | |||
==Pedestrian signals== | |||
* Flashing red: treated as a ]. This can also signal the road is closed. In France, flashing red mandates absolute stop, at the crossing of a railway line, an airport strip, or a swing bridge. | |||
{{Further|Pedestrian crossing}}Pedestrian signals are used to inform pedestrians when to cross a road. Most pedestrian signal heads will have two lights: a 'walk' light (normally a walking human figure, typically coloured green or white) and a 'don't walk' light (normally either a red or orange man figure or a hand), though other variations exist.<ref>{{Cite web|date=25 December 2011|title=Pedestrian Signals|url=https://www.sfbetterstreets.org/find-project-types/pedestrian-safety-and-traffic-calming/pedestrian-signals/|access-date=18 December 2021|website=SF Better Streets|language=en-US}}</ref> | |||
* Flashing yellow: caution, crossing or road hazard ahead. | |||
* Flashing green: varies among jurisdiction. Flashing green can give permission to go straight as well as make a left turn in front of opposing traffic (which is stopped by a steady red light), can indicate the end of a green cycle before the light changes to a solid yellow, or (as in British Columbia, Canada) indicates the intersection is a pedestrian crosswalk. | |||
{| class="wikitable mw-collapsible mw-collapsed" | |||
=== Dual aspects === | |||
|+Pedestrian sequences in various countries | |||
{{Expand section|date=March 2010}} | |||
!Country/ies | |||
! scope="col" style="width: 40%;" |Sequence | |||
! scope="col" style="width: 40%;" |Notes | |||
|- | |||
|Australia, New Zealand, Philippines | |||
|Green man: safe to cross | |||
Flashing red man: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely | |||
Red man: do not cross | |||
These have two lights, usually mounted vertically. They are often seen at railway crossings, fire stations, and at intersections of streets. They flash yellow when cross traffic is not expected, and turn red to stop traffic when cross traffic occurs (e.g., the fire engines are about to exit the station). They are also used on ramp metering, where motorists enter a freeway in heavy traffic. Only one vehicle on the ramp proceeds when the signal shows green. | |||
|Several intersections in Wellington, New Zealand, have alternative green man figures. Eight intersections near ] have silhouettes of ] ],<ref>{{cite news |last=Maoate-Cox |first=Daniela |date=11 September 2014 |title=Kate Sheppard lights encourage voting |publisher=Radio New Zealand |url=http://www.radionz.co.nz/news/election-2014/254365/kate-sheppard-lights-encourage-voting |access-date=20 September 2016}}</ref> while four intersections along Cuba Street have silhouettes of drag performer and LGBT rights activist ].<ref>{{cite news |last=Nicoll |first=Jared |date=8 August 2016 |title=Carmen Rupe lighting up Wellington streets once again |work=Stuff.co.nz |url=http://www.stuff.co.nz/national/82951791/Carmen-Rupe-lighting-up-Wellington-streets-once-again |access-date=20 September 2016}}</ref> | |||
=== Three or more aspects & positioning of aspects === | |||
|- | |||
The standard traffic signal is the red light above the green, with yellow between. | |||
|China | |||
|Green: safe to cross | |||
Red: do not cross | |||
Amber (steady, after green, before red): continue to cross only if unable to stop safely | |||
When the traffic signal with three aspects is arranged horizontally or sideways, the arrangement depends on the ]. In right-lane countries, the sequence is red - yellow - green. In left-lane countries, the sequence is green - yellow - red. | |||
Flashing amber: cross with caution (often used in low-traffic crossing or after midnight) | |||
Other signals are sometimes added for more control, such as for public transportation and right or left turns allowed only when the green arrow is illuminated or specifically prohibited if the red arrow is illuminated. | |||
| | |||
|- | |||
|Japan | |||
|Blue or green man: safe to cross (cyclists may cross or turn left) | |||
Flashing blue or green man: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely | |||
Red standing man: do not cross | |||
Generally, at least one direction of traffic at an intersection has the green light (green aspect) at any moment in the cycle. In some jurisdictions, for a brief time, all signals at an intersection show red at the same time, to clear any traffic in the intersection. The delay can depend on traffic, road conditions, the physical layout of the intersection, and legal requirements. Thus modern signals are built to allow the "all red" in an intersection, even if the feature is not used. | |||
| | |||
|- | |||
|Germany, Czechia, Central Europe | |||
|Green: safe to cross | |||
Amber: continue to cross only if unable to stop safely | |||
Some signals have no "all red" phase: the light turns green for cross traffic the instant the other light turns red.<ref group=note>These are typically older signals. There are many examples in Houston, Texas, of this. Suspended lights constructed so that a single source simultaneously illuminates all four directions always have this characteristic: Red (in two directions) and green (in the two cross directions) with Red-Yellow-Green sequence on two sides and Green-Yellow-Red sequence on the cross sides{{citation needed|date=February 2014}}</ref> | |||
Flashing amber: cross with caution, obey signage (used when lights are out of order or shut down) | |||
===Variations in Canada, Britain, the United States=== | |||
In ] and the ] provinces, lights are often arranged horizontally or sideways, but each aspect takes a different shape: red is a square (larger than the normal circle) and usually in pairs at either end of the fixture, yellow is a diamond, and green is a circle. In ] and many southern and southwestern states, most traffic signals are horizontal in order to ease wind resistance during storms and hurricanes.<ref>{{cite web|title=Traffic Signals|url=http://cityofcarrollton.com/index.aspx?page=259|website=Carrollton Texas|accessdate=12 July 2014}}</ref> | |||
Red: do not cross | |||
In Britain, normal traffic lights follow this sequence: | |||
*Red – stop | |||
*Red and amber (yellow) – stop, indicating it will turn green | |||
*Green – proceed with caution | |||
*Amber – stop if possible to do so | |||
Red and amber: do not cross, prepare for green | |||
===Use of traffic signals in waterways, on railroads for rail traffic=== | |||
|In Germany, ] pedestrian traffic signals have come to be seen as a nostalgic sign for the former ]. | |||
In Germany, the fine for crossing a red light if caught is as of 2019 between €5 and €10.<ref>{{Cite news |last1=Melican |first1=Brian |date=28 January 2014 |title=Why the green man is king in Germany |url=https://www.telegraph.co.uk/expat/expatlife/10599631/Why-the-green-man-is-king-in-Germany.html}}</ref> | |||
|- | |||
|United Kingdom, Ireland, Hong Kong, Switzerland, Macao | |||
|Green walking man: safe to cross | |||
Flashing green man or no man: do not start to cross (only at mid-block crossings); if it appears during crossing, then continue to cross if unable to stop safely | |||
Red standing man: do not cross | |||
The three-aspect standard is also used at ]. Red means that another vessel is passing through. Yellow means that the lock chamber is being emptied or filled to match the level of the approaching vessel. After the gate opens, green means that the vessel may enter. | |||
|In the United Kingdom, there is no direct offence committed if a pedestrian fails to obey crossing signals and many lights commonly only use two still images – a green walking person and a red standing man, this being the general case where the crossing is at a road junction and the pedestrian signals are in combination with those controlling vehicular traffic. | |||
|- | |||
|United States, Canada, Mexico (Tijuana), Philippines (Makati, Davao) | |||
|<u>Formerly signals used the text:</u><ref>{{cite book|section=Section 4D-1 Pedestrian Signal Indications|title=Manual on Uniform Traffic Control Devices, Chapter 4D|url=http://www.trafficsign.us/oldmutcd/1978/4-signals.pdf|edition=6th|version=1986 revision|page=4D-1|publisher=]|publication-date=1978}} See also Figure 4-3 "Pedestrian signal face designs", p. 4D-3.</ref> | |||
WALK<!-- all caps --> | |||
{{Not a typo|DONT}}<!-- no apostrophe --> WALK<!-- all caps --> | |||
Railroad signals, for stopping trains in their own right of way, use the opposite positioning of the colors, the two types cannot be confused.{{citation needed|date=May 2011} That is, green on top and red below is the standard placement of the signal colors on railroad tracks. | |||
<u>Modern version:</u> | |||
==Pedestrian and cyclist crossing lights== | |||
{{Further|Pedestrian crossing}} | |||
{{example farm|section|date=January 2012}} | |||
White walking man: cross with caution | |||
]]] | |||
Flashing ] stophand: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely | |||
===Sounds=== | |||
In some jurisdictions such as Australia and ] pedestrian lights are associated with a sound device, for the benefit of blind and visually impaired pedestrians. These make a slow beeping sound when the pedestrian lights are red and a continuous buzzing sound when the lights are green. In the Australian States of ], ] and ], the sound is produced in the same unit as the push buttons. This system of ] is also widely used at busy intersections in Canadian cities. | |||
Orange stophand: do not enter the intersection | |||
The United Kingdom, the ]s and their predecessor, the ], will make a slow beeping sound to indicate that it is safe to cross the road. The beeping sound is disabled during the night time so as not to disturb any nearby residents.<ref>. 2pass.co.uk.</ref> | |||
|The ] allows an unusual indication variation for pedestrian movement. At signalized intersections without separate pedestrian signal heads, the traffic signals may be programmed to turn red in all directions, followed by a ] indications. During this red-plus-amber indication, the intersection is closed to vehicular traffic and pedestrians may cross, usually in whatever direction they choose. | |||
|- | |||
|Israel | |||
|Red standing man: do not cross; if it appears during crossing, then continue to cross if unable to stop safely | |||
Green walking man: safe to cross | |||
| | |||
|- | |||
|France | |||
| green and light, traditionally and in compliance with the international conventions. | |||
Red Man: Do Not Cross. If it appears during crossing, then continue to cross if unable to stop safely. | |||
Green Man: Safe to Cross. | |||
are polution in control in light something vehicles in Australia and New Zealand=== | |||
| In 2023, a two year experiment was allowed to start on 8 intersections experimenting blinking yellow light and 7 other one frozen yellow light.<ref>{{cite web | url=https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000047501337 | title=Arrêté du 21 avril 2023 portant expérimentation d'une phase jaune de temps de dégagement piéton sur des feux piétons }}</ref> | |||
In Australia and New Zealand, the light sequence is: | |||
|} | |||
*Green man: safe to cross the intersection | |||
*Flashing red man: continue to cross if already in the intersection, but do not start to cross | |||
*Red man: do not cross | |||
], Slovenia]] | |||
Some traffic lights in ], ] and ] have countdown timers for pedestrian crossing lights, usually a countdown from 30 when the red flashing man appeared. Countdown timers have been installed on some pedestrian crossing lights in ] counting down from 15 seconds. | |||
Where pedestrians need to cross the road between junctions, a signal-controlled crossing may be provided as an alternative to a ] or uncontrolled crossing. Traffic lights are normally used at crossings where vehicle speeds are high, where either vehicle or pedestrian flows are high or near signalised junctions.<ref name=":1" />{{Rp|location=c.18}} In the UK, this type of crossing is called a ], though more modern iterations are puffin and pedex crossings. In the UK, these crossings normally need at least four traffic signals, which are of a regular type (red, amber, and green), two facing in each direction. Furthermore, pedestrians will be provided with push buttons and pedestrian signals, consisting of a red and green man. Farside signals are located across the crossing, while nearside signals are located below the traffic lights, facing in the direction of oncoming traffic.<ref name=":1" />{{Rp|location=c.18}} A ] is a special type of traffic used in the US at mid-block crossings. These consist of two red signals above a single amber signal. The beacon is unlit until a pedestrian pushes the cross button. Then an amber light will show, followed by both red lights, at which point the 'Walk' symbol will illuminate for pedestrians. At the end of the crossing phase, the 'Don't Walk' symbol will flash, as will the amber traffic light.<ref>{{Cite web|title=New traffic signals make it safer for pedestrians |url=https://usatoday30.usatoday.com/news/nation/2010-08-09-crosswalk09_ST_N.htm|access-date=19 December 2021|website=USA Today}}</ref>], in Tokyo, is a famous example of a ] with diagonal crossings.]] | |||
Pedestrians are usually incorporated into urban signalised junctions in one of four ways: no facilities, parallel walk, walk with traffic, or all-red stages. No facilities may be provided if pedestrian demand is low, in areas where pedestrians are not permitted, or if there is a subway or overpass. No provision of formal facilities means pedestrians will have to self-evaluate when it is safe to cross, which can be intimidating for pedestrians.<ref name=":1" />{{Rp|page=71}} With a "parallel walk" design, pedestrians walk alongside the traffic flow. A ] may be provided, whereby pedestrians get a "walk" signal before the traffic gets a green light, allowing pedestrians to establish themselves on the crossing before vehicles begin to turn, to encourage drivers to give way.<ref>{{Cite web|date=17 November 2017|title=Leading Pedestrian Interval|url=https://www.toronto.ca/services-payments/streets-parking-transportation/traffic-management/traffic-signals-street-signs/types-of-traffic-signals/leading-pedestrian-interval-phase/|access-date=19 December 2021|website=City of Toronto|language=en-CA}}</ref> A 'walk with traffic' facility allows pedestrians to go at the same time as other traffic movements with no conflict between movements. This can work well on one-way roads, where turning movements are banned or where the straight-ahead movement runs in a different stage from the turning movement. A splitter island could also be provided. Traffic will pass on either side of the island and pedestrians can cross the road safely between the other flows.<ref name=":1" />{{Rp|page=72|pages=}} | |||
An all-red stage, also known as a full pedestrian stage, a ] or a Barnes Dance,{{Efn|The Barnes Dance is named after an American traffic engineer, ]. Barnes did not claim to have invented the system but was a strong advocate of it, having observed the difficulties his daughter faced crossing the road to get to school.}} holds all vehicular traffic at the junction to allow pedestrians time to safely cross without conflict from vehicles. It allows allows the use of diagonal crossings. This may require a longer cycle time and increase pedestrian wait periods, though the latter can be eased by providing two pedestrian stages.<ref name=":1" />{{Rp|page=|pages=71–72}}] | |||
Some traffic-light controlled junctions have a light sequence that stops all vehicular traffic at the junction at the same time, and gives pedestrians exclusive access to the intersection so that they can cross in any direction (including diagonally). This is prominently featured in the Sydney CBD outside town hall. This is known as a "]" or Barnes Dance in some places. In New Zealand such pedestrian crossings can be found in the central business district (CBD) of Auckland, ] and ]. | |||
Pedestrian countdown timers are becoming common at urban signal-controlled crossings. Where a pedestrian countdown is shown, it is normally used in conjunction with the flashing hand signal (in the US and Canada) or blackout period (UK), showing the amount of time remaining in seconds until the end of the flashing hand or blackout.<ref name=":1" /><ref name=":8">{{Cite journal |last=Schmitz |first=Jacob |date=1 July 2011 |title=The Effects of Pedestrian Countdown Timers on Safety and Efficiency of Operations at Signalized Intersections |url=https://digitalcommons.unl.edu/civilengdiss/28 |journal=Civil and Environmental Engineering Theses, Dissertations, and Student Research}}</ref> Pedestrian countdown timers do not significantly increase or reduce the number of red- and amber-light running drivers. Studies have found that pedestrian countdown timers do significantly improve pedestrian compliance over traditional pedestrian signals; however, results are mixed.<ref name=":8" /><ref>{{Cite journal |last1=Kłos |first1=Marcin Jacek |last2=Sobota |first2=Aleksander |last3=Żochowska |first3=Renata |last4=Karoń |first4=Grzegorz |date=11 September 2020 |title=Effects of countdown timers on traffic safety at signalized intersections |journal=Transactions on Transport Sciences |volume=11 |issue=2 |pages=19–27 |doi=10.5507/tots.2020.010 |s2cid=225185972 |issn=1802-971X|doi-access=free }}</ref>{{Clear}} | |||
===Smartphone Zombie ribbon=== | |||
The Barnes Dance is named after an American traffic engineer, Henry A. Barnes. Barnes did not claim to have invented the system but was a strong advocate of it, having observed the difficulties his daughter faced crossing the road to get to school.<ref>{{cite web|url=http://www.nzhistory.net.nz/page/auckland-pedestrians-begin-%26%23039%3Bbarnes-dance%26%23039%3B|title=Auckland pedestrians begin 'Barnes Dance' - NZHistory, New Zealand history online|work=nzhistory.net.nz}}</ref> | |||
As the 12 to 45% of pedestrian deaths caused by 'pedestrian distraction' has been linked to cell phone usage,<ref>{{Cite web |title=Smartphone texting linked to compromised pedestrian safety |url=https://www.sciencedaily.com/releases/2020/02/200203210601.htm |access-date=2024-06-08 |website=ScienceDaily |language=en}}</ref> some cities (including ], ], ], ], ], and ]) have installed LED strips embedded in the sidewalk before crosswalks to warn distracted pedestrians of immanent pedestrian crossings.<ref>{{Cite web |last=Broom |first=Douglas |date=November 1, 2021 |title=Zombie traffic lights' are saving the lives of smartphone users - here's how |url=https://www.weforum.org/agenda/2021/11/saving-lives-smartphone-zombies-pedestrians/ |access-date=June 8, 2024 |website=World Economic Forum}}</ref> This additional signal, which is synchronized with conventional signals, aims to decrease injury rates by telling distracted pedestrians when it is safe to cross the road without them having to lift their head. | |||
<gallery> | |||
File:Korean smartphone zombie pedestrian traffic light green.jpg|] light in green | |||
File:Korean smartphone zombie pedestrian traffic light green close up.jpg|Smartphone zombie light in green, close up | |||
File:Korean smartphone zombie pedestrian traffic light red.jpg|Smartphone zombie light in red | |||
File:Korean smartphone zombie pedestrian traffic light red close up.jpg|Smartphone zombie light in red, close up | |||
</gallery> | |||
=== |
===Auditory and tactile signals=== | ||
In some jurisdictions such as Australia, pedestrian lights are associated with a sound device, for the benefit of blind and visually impaired pedestrians. These make a slow beeping sound when the pedestrian lights are red and a continuous buzzing or fast beeping sound when the lights are green. In the Australian States of ], ], ], and ], the sound is produced in the same unit as the push buttons. In a circle above the button, the sound is produced and can be felt along with a raised arrow that points in the direction to walk.<ref>{{Cite web|last=Park |first=Miles|title=Sublime design: the PB/5 pedestrian button|url=http://theconversation.com/sublime-design-the-pb-5-pedestrian-button-26232|access-date=19 December 2020|website=The Conversation|date=29 June 2014 }}</ref> This system of ] is also widely used at busy intersections in Canadian cities. In the United Kingdom, the ]s and their predecessor, the ], will make a fast beeping sound to indicate that it is safe to cross the road. The beeping sound is disabled during the nighttime so as not to disturb any nearby residents.<ref>. 2pass.co.uk.</ref> | |||
] | |||
The European approach to a signalized crossing is to use dual or, more rarely, a triple aspect<ref>{{cite web |title=Freewebs.com |url=http://web.archive.org/web/20100105033713/http://www.freewebs.com/trafficlightsignals2/euroheads.htm }}</ref> with a blackened out lens of a ] pedestrian. For cyclists, the same approach is used, with the lens blackened out for a bicycle frame. It is not uncommon to see lenses with both symbols on them. Most European countries use orange instead of yellow for the middle light. | |||
In some states in the United States, at some busy intersections, buttons will make a beeping sound for blind people. When the light changes, a speaker built into the button will play a recording to notify blind people that it is safe to cross. When the signal flashes red, the recording will start to count down with the countdown timer. In several countries such as New Zealand, technology also allows deaf and blind people to feel when lights have changed to allow safe crossing. A small pad, housed within an indentation in the base of the box housing the button mechanism, moves downwards when the lights change to allow crossing. This is designed to be felt by anyone waiting to cross who has limited ability to detect sight or sound. In Japan, a traffic light emits an electronic sound that mimics the sound of birdsong to help the visually impaired. Some traffic lights fix the order and type of sound so that they can tell which direction is a green light. In general, "''Piyo''" (peep) and "''Piyo-piyo''", which is a small bird call, and "''Kakkō''" and "''Ka-kakkō''", which is a cuckoo call, are associated with this system.<ref>{{Cite web|title=横断歩道、減る「通りゃんせ」 音響信号「ピヨピヨ」化:朝日新聞デジタル|url=https://www.asahi.com/articles/ASJ9N3VTNJ9NTIPE00Z.html|access-date=1 September 2020|website=朝日新聞デジタル|language=ja|archive-date=6 November 2020|archive-url=https://web.archive.org/web/20201106132038/https://www.asahi.com/articles/ASJ9N3VTNJ9NTIPE00Z.html|url-status=dead}}</ref> Some pedestrian crossings in Lithuania make a slow beeping sound indicating that the traffic light is about to turn off. | |||
The light sequence is: | |||
*Green: safe to cross. | |||
*Yellow or orange: continue to cross only if unable to stop safely. | |||
*Flashing yellow or orange: cross with caution (often used when lights are out of order or shut down). | |||
*Red: do not cross. | |||
== Cycle signals == | |||
In Germany, the Czech Republic and some other Central European countries, a combination of red and orange lights is used just before the switch back to green. It allows drivers to stop their engines during the red light. The light sequence is as follows:{{Citation needed|date=March 2012}} | |||
{{Further|Protected intersection}} | |||
*Green: safe to cross. | |||
] | |||
*Orange: continue to cross only if unable to stop safely. | |||
] | |||
*Flashing orange: cross with caution, obey signage (used when lights are out of order or shut down). | |||
Where cycle lanes or cycle tracks exist on the approach to a signal-controlled junction, it must be considered how to incorporate cyclists safely into the junction to reduce conflict between motor vehicles and cyclists. | |||
*Red: do not cross. | |||
*Red and orange: do not cross, prepare for green. | |||
An ] can be placed after the stop line at traffic lights. This allows cyclists to position themselves in front of traffic at a red light and get a headstart.<ref>{{Cite web|title=Advanced Stop Line {{!}} Cycling Embassy of Great Britain|url=https://www.cycling-embassy.org.uk/dictionary/advanced-stop-line|access-date=19 December 2021|website=www.cycling-embassy.org.uk}}</ref> | |||
The light is blackened out with a pedestrian pictogram. | |||
In the US, design advice typically advises that the cycle lane should continue through the junction to the left of the right-turn lane; however, this creates conflict where motor vehicles wish to enter the right lane, as they must cross the cycle lane at a bad angle.<ref name=":2">{{Citation|last=Dutch|first=Bicycle|title=Junction design, the Dutch – cycle-friendly – way |date=3 April 2011|url=https://www.youtube.com/watch?v=FlApbxLz6pA|work=YouTube|language=en|access-date=18 December 2021}}</ref> | |||
] pedestrian traffic signals have come to be seen as a nostalgic sign for the former ]. | |||
Under Dutch engineering principles, cyclists are instead kept to the right of the junction, with protected kerbs. This improves safety by putting cyclists into the eyeline of motor vehicles at the stop line, allowing cyclists a headstart over turning traffic. This design also allows cyclists to complete far-side turns without having to wait in the centre of the junction.<ref name=":2"/> UK engineers have innovated on this design through the Cycle Optimised Protected Signals (CYCLOPS) junction, e.g. in ]. This places the cycle track around the edge of the signal junction and gives cyclists and pedestrians a single all-red phase, entirely separate from motor traffic and shortens pedestrian crossing times.<ref>{{Cite web|title=Manchester opens UK's first CYCLOPS cycling junction|url=https://www.intelligenttransport.com/transport-news/101901/manchester-opens-uks-first-cyclops-cycling-junction/|access-date=18 December 2021|website=Intelligent Transport|language=en}}</ref> | |||
===British standard=== | |||
In the United Kingdom, Ireland, ] and dependent territories, and former possessions like Hong Kong two or more of the following signals are displayed to pedestrians - | |||
:* A still image of a green walking man: cross the road | |||
:* Flashing green walking man: continue to cross if already on the crossing but do not start to cross. | |||
::* Some signals use an amber numerical countdown display, instead of the flashing green man, to show how long people already crossing have remaining before the red standing man shows, and traffic is given a green signal | |||
:* Red standing man: do not cross/do not start to cross | |||
Alternatively, cyclists can be considered pedestrians on approach to a junction, or where a cycle track crosses a road and combined pedestrian-cyclist traffic lights (known as ]s in the UK) can be provided.<ref>{{Cite web|title=What is a Toucan crossing?|url=https://www.autoexpress.co.uk/car-news/105228/what-is-a-toucan-crossing|access-date=19 December 2021|website=Auto Express|language=en}}</ref> | |||
In the United Kingdom there is no direct offense committed if a pedestrian fails to obey crossing signals and many lights commonly only use two still images - a green walking man and a red standing man, this being the general case where the crossing is at a road junction and the pedestrian signals are in combination with those controlling vehicular traffic. Flashing amber lights and images at pedestrian crossings are used where the vehicular traffic lights perform the sole function of stopping road traffic to allow pedestrians to cross a road. | |||
== Public transport signals == | |||
The same system is used also in ] and ].{{citation needed|date=August 2014}}{{Clarify|reason=why should "British standard" have been used in a Portuguese colony? And do we want to organize/ise this article this way? Including Hong Kong, above|date=March 2012}} | |||
Traffic lights for public transport often use signals that are distinct from those for private traffic. They can be letters, arrows or bars of white or (an LED 100-] typical) coloured light. | |||
=== Transit signals in North America === | |||
===China standard=== | |||
{|class="wikitable" style="float:right;text-align:center;font-size:70%;width:20em;" | |||
*Green: safe to cross. | |||
|+MUTCD Fig. 8C-3 | |||
*Red: do not cross. | |||
| | |||
*Yellow(Solid, after Green, before Red): continue to cross only if unable to stop safely. | |||
! colspan=5 | Three-lens signal !! colspan=5 | Two-lens signal | |||
*Flashing yellow: cross with caution (often used in low-traffic crossing or after mid-night). | |||
|- | |||
! rowspan=3 | ]<br />Single LRT route | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
| colspan=5 | | |||
|- | |||
| Prepare to stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || (flashing) | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
|- | |||
| Go || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
| Go || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || {{efn-lr|name=2prep|"Go" lens may be used in flashing mode to indicate "prepare to stop"}} | |||
|- | |||
| style="font-size:25%;background:#888;" colspan=11 | | |||
|- | |||
! rowspan=3 | ]<br />Two LRT route diversion | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
| colspan=5 | | |||
|- | |||
| Prepare to stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || (flashing) | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
|- | |||
| Go || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | ] || {{efn-lr|name=samehouse|Could be in single housing}} | |||
| Go || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | ] || {{efn-lr|name=2prep}}{{efn-lr|name=samehouse}} | |||
|- | |||
| style="font-size:10%;background:#888;" colspan=11 | | |||
|- | |||
! rowspan=3 | ]<br />Two LRT route diversion | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
| colspan=5 | | |||
|- | |||
| Prepare to stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || (flashing) | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
|- | |||
| Go || style="background:#aaa;" | ] || style="background:#aaa;" | ] || style="background:#aaa;" | || {{efn-lr|name=samehouse}} | |||
| Go || style="background:#aaa;" | ] || style="background:#aaa;" | ] || style="background:#aaa;" | || {{efn-lr|name=2prep}}{{efn-lr|name=samehouse}} | |||
|- | |||
| style="font-size:25%;background:#888;" colspan=11 | | |||
|- | |||
! rowspan=3 | ]<br />Three LRT route diversion | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
| colspan=5 | | |||
|- | |||
| Prepare to stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || (flashing) | |||
| Stop || style="background:#aaa;" | || style="background:#aaa;" | ] || style="background:#aaa;" | || | |||
|- | |||
| Go || style="background:#aaa;" | ] || style="background:#aaa;" | ] || style="background:#aaa;" | ] || {{efn-lr|name=samehouse}} | |||
| Go || style="background:#aaa;" | ] || style="background:#aaa;" | ] || style="background:#aaa;" | ] || {{efn-lr|name=2prep}}{{efn-lr|name=samehouse}} | |||
|- | |||
| colspan=11 style="text-align:left;" | '''Notes'''<br />{{notelist-lr}} | |||
|} | |||
] specifies a standard vertically oriented signal with either two or three lenses, displaying white lines on a black background.<ref>{{MUTCD |year=2009 |revision=3 |chapter=8C}}</ref>{{rp|Fig.8C-3}} | |||
Some systems use the letter B for buses and T for trams. The ] light rail system in ], the ] in ], and the ] Streetcar System in ] use a simplified variant of the Belgian/French system in the respective city's central business district where only the "go" and "stop" configurations are used. A third signal equal to amber is accomplished by flashing the "go" signal. | |||
===North American standard=== | |||
]]] | |||
In the United States, the most common aspect is the written 'walk' or 'don't walk.' In Canada, the white walking man is almost always used. Increasingly for retrofits of dual aspects and newer installations, the lower aspect formerly used for the "walk" signal (a walking person) is being replaced with a timer countdown. The raised hand pictogram first appeared in the city of Westmount, Montreal, and was invented by Alexander Heron, having observed a policeman's gloved hand controlling a crossing.{{Citation needed|date=January 2013}} | |||
=== Public transport signals in Europe === | |||
The light sequence is: | |||
In some European countries and ], dedicated traffic signals for public transport (tram, as well any that is using a ]) ] four white lights that form the letter T.{{Citation needed|date=December 2009}} If the three top lamps are lit, this means "stop". If the bottom lamp and some lamps on the top row are lit, this means permission to go in a direction shown. In the case of a tram signal, if there are no tram junctions or turns at an intersection, a simpler system of one amber signal in the form of the letter T is used instead; the tram must proceed only when the signal is lit. | |||
* Green, blue, or white walking human or "walk": cross with caution (pedestrians have the right of way; motorists turning left or right must yield to pedestrians). | |||
* Flashing red or orange stop hand or "don't walk": do not start crossing, but continue if already in the middle of the intersection. | |||
*Red or orange stop hand or "don't walk": do not enter the intersection | |||
In North European countries, the tram signals feature white lights of different forms: "S" for "stop", "—" for "caution" and arrows to permit passage in a given direction.<ref>{{Cite web|url=http://www.trafikverket.se/TrvSeFiler/Foretag/Bygga_och_underhalla/Vag/Vagutformning/Dokument_vag_och_gatuutformning/Vagar_och_gators_utformning/Trafiksignaler/04_utrustning_trafiksignaler.pdf|title=Publication on traffic lights the from the Swedish Transport Administration|access-date=25 August 2011|archive-date=23 September 2016|archive-url=https://web.archive.org/web/20160923032057/http://www.trafikverket.se/TrvSeFiler/Foretag/Bygga_och_underhalla/Vag/Vagutformning/Dokument_vag_och_gatuutformning/Vagar_och_gators_utformning/Trafiksignaler/04_utrustning_trafiksignaler.pdf|url-status=dead}}</ref> In Sweden, All signals use white lighting and special symbols ("S", "–" and an arrow) to distinguish them from regular signals. | |||
The ] allows an unusual indication variation for pedestrian movement. At signalized intersections without separate pedestrian signal heads, the traffic signals may be programmed to turn red in all directions, followed by a steady display of yellow lights simultaneously with the red indications. During this red-plus-yellow indication, the intersection is closed to vehicular traffic and pedestrians may cross, usually in whatever direction they choose (this is known as a "]").{{Citation needed|date=March 2014}} | |||
The ] uses a distinctive "negenoog" (nine-eyed) design shown on the top row of the diagram;<ref>{{in lang|nl}} Official regulation of traffic rules and traffic signs</ref> bottom row signals are used in ], Luxembourg, France, and Germany. The signals mean (from left to right): "go straight ahead", "go left", "go right", "go in any direction" (like the "green" of a normal traffic light), "stop, unless the emergency brake is needed" (equal to "amber"), and "stop" (equal to "red"). | |||
== Lights for public transport == | |||
] | |||
] | |||
=== Public transport signals in the Asia-Pacific region === | |||
] traffic light (left) for use by ] vehicles only. All signals use white lighting and special symbols ("S","–" and an arrow) to distinguish them from regular signals. The small light at the top tells the driver when the vehicle's ] signal is received by the traffic light]] | |||
In Japan, tram signals are under the regular vehicle signal; however, the colour of the signal intended for trams is orange. The small light at the top tells the driver when the vehicle's ] signal is received by the traffic light. In Hong Kong, an amber T-signal is used for trams, in place of the green signal. In addition, at any tramway junction, another set of signals is available to indicate the direction of the tracks. In Australia and New Zealand, a white "B" or "T" sometimes replaces the green light indicating that buses or trams (respectively) have right of way.<gallery> | |||
Traffic lights for public transport often use signals that are distinct from those for private traffic. They can be letters, arrows or bars of white or colored light. | |||
File:HK Causeway Bay tram traffic lights Aug-2017.jpg|T signal (trams) in Hong Kong | |||
File:Karlsruhe Ebertstr-Karlstr Tramampeln.jpg|Bus and tram signals in ], ] | |||
</gallery> | |||
=== Preemption and priority === | |||
In ], the tram signals feature an orange horizontal bar and a white vertical bar.{{Citation needed|date=December 2009}} Some systems use the letter B for buses, and T for trams. | |||
In some European countries and ], dedicated traffic signals for public transport (tram, as well any that is using a ]) ] four white lights that form the letter T.{{Citation needed|date=December 2009}} If the three top lamps are lit, this means "stop". If the bottom lamp and some lamps on the top row are lit, this means permission to go in a direction shown. In case of a tram signal, if there are no tram junctions and turns on an intersection, a simpler system of one yellow signal in the form of letter T is used instead; the tram must proceed only when the signal is lit. | |||
In North European countries, the tram signals feature white lights of different forms: "S" for "stop", "—" for "caution" and arrows to permit passage in a given direction.<ref></ref> | |||
] | |||
The ] use a distinctive "negenoog" (nine-eyed) design shown on the top row of the diagram;<ref>{{nl}} Official regulation of traffic rules and traffic signs</ref> bottom row signals are used in ], France and Germany. The signals mean (from left to right): "go straight ahead", "go left", "go right", "go in any direction" (like the "green" of a normal traffic light), "stop, unless the emergency brake is needed" (equal to "yellow"), and "stop" (equal to "red"). | |||
The ] light rail system in ] as well as the ] Streetcar System in ] use a simplified variant of the Belgian/French system in the respective city's central business district where only the "go" and "stop" configurations are used. A third signal equal to yellow is accomplished by flashing the "go" signal. | |||
In Japan, tram signals are under the regular vehicle signal; however the color of the signal intended for trams is orange. | |||
In Hong Kong Island, Hong Kong, a yellow T-signal is used for trams, in place of the green signal. Addition to that, at any tramway junction, another set of signals is available to indicate the direction of the tracks. | |||
In Australia a white "B" or "T" sometimes replaces the green light indicating that buses or trams (respectively) have right of way. | |||
=== Preemption and priority ===1234 dfuygdf asdjkgg aLkkf sca kjf vclkjjgc gc0000 | |||
{{Main|Traffic signal preemption|Bus priority}} | {{Main|Traffic signal preemption|Bus priority}} | ||
Some regions have signals that are interruptible, giving priority to special traffic usually ]s such as ], ambulances, and police ].<ref>{{cite web |title=Emergency vehicle traffic signal preemption system |work=United States Patent and Trademark Office |url=http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=6326903| accessdate=7 October 2005}}</ref><ref>{{cite web|url=http://mutcd.fhwa.dot.gov/HTM/2003r1/part4/part4f.htm|title=FHWA - MUTCD - 2003 Edition Revision 1 Chapter 4F|work=dot.gov}}</ref> Most of the systems operate with small transmitters that send radio waves, ] signals, or ] signals that are received by a sensor on or near the traffic lights. Some systems use audio detection, where a certain type of siren must be used and detected by a receiver on the traffic light structure. | |||
Some regions have signals that are interruptible, giving priority to special traffic, usually ]s such as ], ]s, and ]s.<ref>{{cite web |title=Emergency vehicle traffic signal preemption system |work=United States Patent and Trademark Office |url=http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=6326903 |access-date=7 October 2005 |archive-date=21 December 2016 |archive-url=https://web.archive.org/web/20161221033705/http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=6326903 |url-status=dead }}</ref><ref>{{cite web|url=https://mutcd.fhwa.dot.gov/HTM/2003r1/part4/part4f.htm|title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4F|work=dot.gov}}</ref> Most of the systems operate with small transmitters that send radio waves, ] signals, or ] signals that are received by a sensor on or near the traffic lights. Some systems use audio detection, where a certain type of siren must be used and detected by a receiver on the traffic light structure. | |||
Upon activation the normal traffic light cycle is suspended and replaced by the "preemption sequence": the traffic lights to all approaches to the intersection are switched to "red" with the exception of the light for the vehicle that has triggered the preemption sequence. Sometimes, an additional signal light is placed nearby to indicate to the preempting vehicle that the preempting sequence has been activated and to warn other motorists of the approach of an emergency vehicle. The normal traffic light cycle resumes after the sensor has been passed by the vehicle that triggered the preemption. | |||
Upon activation, the normal traffic light cycle is suspended and replaced by the "preemption sequence": the traffic lights to all approaches to the intersection are switched to "red" with the exception of the light for the vehicle that has triggered the preemption sequence. Sometimes, an additional signal light is placed nearby to indicate to the preempting vehicle that the preempting sequence has been activated and to warn other motorists of the approach of an emergency vehicle. The normal traffic light cycle resumes after the sensor has been passed by the vehicle that triggered the preemption. | |||
In lieu of preemptive mechanisms, in most jurisdictions, emergency vehicles are not required to respect traffic lights. However, emergency vehicles must slow down, proceed cautiously and activate their emergency lights to alert oncoming drivers to the preemption when crossing an intersection against the light.<ref>{{cite web|title=Emergency Vehicles at Red Signal or Stop Sign|url=http://codes.ohio.gov/orc/4511.03|website=Ohio Laws and Rules|accessdate=22 July 2014}}</ref><ref>{{cite web|title=Emergency Service and Vehicles|url=https://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+46.2-920|website=Virginia General Assembly|accessdate=22 July 2014}}</ref> | |||
In lieu of preemptive mechanisms, in most jurisdictions, emergency vehicles are not required to respect traffic lights. However, emergency vehicles must slow down, proceed cautiously and activate their emergency lights to alert oncoming drivers to the preemption when crossing an intersection against the light.<ref>{{cite web|title=Emergency Vehicles at Red Signal or Stop Sign|url=http://codes.ohio.gov/orc/4511.03|website=Ohio Laws and Rules|access-date=22 July 2014}}</ref><ref>{{cite web|title=Emergency Service and Vehicles|url=https://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+46.2-920|website=Virginia General Assembly|access-date=22 July 2014}}</ref> | |||
Unlike preemption, which immediately interrupts a signal's normal operation to serve the preempting vehicle and is usually reserved for emergency use, "]" is a set of strategies intended to reduce delay for specific vehicles, especially mass transit vehicles such as buses. A variety of strategies exist to give priority to transit but they all generally work by detecting approaching transit vehicles and making small adjustments to the signal timing. These adjustments are designed to either decrease the likelihood that the transit vehicle will arrive during a red interval or decrease the length of the red interval for those vehicles that are stopped. Priority does not guarantee that transit vehicles always get a green light the instant they arrive like preemption does. | |||
Unlike preemption, which immediately interrupts a signal's normal operation to serve the preempting vehicle and is usually reserved for emergency use, "]" is a set of strategies intended to reduce delay for specific vehicles, especially mass transit vehicles such as buses. A variety of strategies exist to give priority to transit but they all generally work by detecting approaching transit vehicles and making small adjustments to the signal timing. These adjustments are designed to either decrease the likelihood that the transit vehicle will arrive during a red interval or decrease the length of the red interval for those vehicles that are stopped. Priority does not guarantee that transit vehicles always get a green light the instant they arrive as preemption does. | |||
== Turning signals and rules == | |||
== Operation == | |||
], on State Route 25. Notice the red arrow to the left of the two green straight lights.]] | |||
{{Main|Traffic light control and coordination}} | |||
In some instances, traffic may turn left (in left-driving jurisdictions) or right (in right-driving jurisdictions) after stopping at a red light, providing they give way to the pedestrians and other vehicles. In some places that generally disallow this, a sign next to the traffic light indicates that it is allowed at a particular intersection.<ref>. Rta.nsw.gov.au.</ref> Conversely, jurisdictions that generally allow this might forbid it at a particular intersection with a "no turn on red" sign, or put a green arrow to indicate specifically when a turn is allowed without having to ] to pedestrians (this is usually when traffic from the perpendicular street is making a turn onto one's street and thus no pedestrians are allowed in the intersection anyway). Some jurisdictions allow turning on red in the opposite direction (left in right-driving countries; right in left-driving countries) from a one-way road onto another one-way road; some of these even allow these turns from a two-way road onto a one-way road.<ref> para 3a.</ref> Also differing is whether a red arrow prohibits turns; some jurisdictions require a "no turn on red" sign in these cases. A study in the ] (a right-driving jurisdiction) concluded that allowing drivers to proceed straight on red after stopping, at specially posted T-intersections where the intersecting road went left only, was dangerous.{{Citation needed|date=October 2009}} Proceeding straight on red at T-intersections where the intersecting road went left only used to be legal in ], with right-hand traffic provided that such movement would not interfere with other traffic, but when the ] took effect on 1 May 2004, such movement was outlawed.<ref>{{cite web|url=http://www.geocities.com/jusjih/trafficlightsignals.html#turnred |title=Traffic Light Signals and Red Light Cameras |publisher=Geocities.com |accessdate=2009-05-19|archiveurl=http://web.archive.org/web/20091024221040/http://geocities.com/jusjih/trafficlightsignals.html|archivedate=24 October 2009}}</ref> In some other countries, the permission is indicated by a flashing yellow arrow (cars do not have to stop but must give way to other cars and pedestrians). | |||
] | |||
A variety of different control systems are used to operate signal cycles smoothly, ranging from simple clockwork mechanisms to sophisticated computerised control systems. Computerised systems are normally ], i.e. controlled by ] or other sensors on junction approaches. Area-wide coordination can allow ] systems to be set up for vehicles or cycle tracks.<ref name="progr">{{cite web |last=Robinson |first=Larry |title=Traffic Signal Progression |url=http://midimagic.sgc-hosting.com/progreso.htm |access-date=22 May 2014}}</ref> ] systems combine traditional actuation, a wider array of sensors and ] to further improve performance of signal systems.<ref>{{Cite web |date=18 May 2022 |title=Going Nowhere Fast? Smart Traffic Lights Can Help Ease Gridlock |url=https://science.howstuffworks.com/engineering/civil/smart-traffic-lights-news.htm |access-date=4 February 2023 |website=HowStuffWorks |language=en-us}}</ref> A traffic signal junction or crossing is typically controlled by a ] mounted inside a cabinet nearby.<ref name="ts101"> {{Webarchive|url=https://web.archive.org/web/20210228141151/http://www.dot.state.mn.us/trafficeng/publ/signals101/index.html |date=28 February 2021 }}, ], 2006</ref> | |||
"Phases" (or "signal groups" in Australia and New Zealand) are indications show simultaneously, e.g. multiple green lights which control the same traffic approach. A "movement" is any path through the junction which vehicles or pedestrians are permitted to take, which is "conflicting" if these paths cross one another. A stage (or "phase" in ANZ) is a group of non-conflicting phases which move at the same time. The stages are collectively known as a "cycle".<ref name=":0">{{Cite web |title=Traffic Signal Design Terminology |url=https://www.traffic-signal-design.com/traffic-signal-design-terminology.htm |access-date=2 October 2022 |website=www.traffic-signal-design.com |language=en}}</ref> The time between two conflicting green phases is called an "intergreen period", which is set at an appropriate length for the junction to safely clear, especially for turning traffic which may be waiting in the centre of the junction. This often results in an all red stage, when all approaches are shown a red light and no vehicle can proceed. This all red is sometimes extended to allow a ], where pedestrians can cross the empty junction in any direction all at once.<ref>DfT Traffic Advisory Leaflet 1/06, Part 4 – https://tsrgd.co.uk/pdf/tal/2006/tal-1-06_4.pdf</ref> Some signals have no "all red" phase: the light turns green for cross traffic the instant the other light turns red.{{efn|These are typically older signals. There are many examples in Houston, Texas, of this. Suspended lights constructed so that a single source simultaneously illuminates all four directions always have this characteristic: Red (in two directions) and green (in the two cross directions) with Red-Yellow-Green sequence on two sides and Green-Yellow-Red sequence on the cross sides{{citation needed|date=February 2014}} }} | |||
Another distinction is between intersections that have dedicated signals for turning across the flow of opposing traffic and those that do not. Such signals are called dedicated left-turn lights in the United States and Canada (since opposing traffic is on the left). With dedicated left turn signals, a left-pointing arrow turns green when traffic may turn left without opposing traffic and pedestrian conflict, and turns red or disappears otherwise. Such a signal is referred to as a "protected" signal if it has its own red phase; a "permissive" signal does not have such a feature. Three standard versions of the permissive signal exist:{{Citation needed|date=December 2009}} One version is a horizontal bar with five lights – the green and yellow arrows are located between the standard green and yellow lights. A vertical five-light bar holds the arrows underneath the standard green light (in this arrangement, the yellow arrow is sometimes omitted, leaving only the green arrow below the solid green light, or possibly an ] based device capable of showing both green and yellow arrows within a single lamp housing). Some newer LED turn arrows seen in parts of Canada are capable of multicolored animation. Such lights will often display a flashing and animated green or yellow arrow when the dedicated turn is allowed, but then transform into a red arrow on a white background with a red line through it, emphasising that the turn is no longer allowed. These lights will also often have the words "no turn" displayed, or an explanatory reason why the turn is not allowed, such as "train" in the case of a rail or light rail crossing. A third type is known as a "doghouse" or "cluster head" – a vertical column with the two normal lights is on the right side of the signal, a vertical column with the two arrows is located on the left, and the normal red signal is in the middle above the two columns. Cluster signals in Australia and ] use six signals, the sixth being a red arrow that can operate separately from the standard red light. In a fourth type, sometimes seen at intersections in ] and ], there is no dedicated left-turn lamp per se. Instead, the normal green lamp flashes rapidly, indicating permission to go straight as well as make a left turn in front of opposing traffic, which is being held by a steady red lamp. (This "advance green," or flashing green can be somewhat startling and confusing to drivers not familiar with this system. This also can cause confusion amongst visitors to British Columbia, where a flashing green signal denotes a pedestrian controlled crosswalk.)<ref>{{PDFlink|}} Accessed: 25 March 2014</ref> Another interesting practice seen at least in Ontario is that cars wishing to turn left that arrived after the left turn signal ended can do so during the yellow phase, as long as there is enough time to make a safe turn. | |||
Many traffic light installations are fitted with vehicle actuation, i.e. detection, to improve the flexibility of traffic systems to respond to varying traffic flows. Detectors come in the form of ]s fitted to the signal heads or ]s within the road surface. Induction loops are beneficial due to their smaller chance of breakdown, but their simplicity can limit their ability to handle some situations, particularly involving lighter vehicles such as motorcycles or pedal cycles.<ref>{{cite web |date=April 2000 |title=How does a traffic light detect that a car has pulled up and is waiting for the light to change? |url=https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/how-does-a-traffic-light-detect-that-a-car-has-pulled-up-and-is-waiting-for-the-light-to-change.htm |access-date=7 January 2021 |website=Howstuffworks}}</ref> This situation most often occurs at times of day when other traffic is sparse as well as when the small vehicle is coming from a direction that does not have a high volume of traffic.<ref>{{cite web |title=Motorcycles And Stoplights |url=http://motorcycleassistant.com/motorcycles-and-stoplights/ |website=Motorcycle Assistant}}</ref> | |||
A flashing yellow arrow, which allows drivers to make left turns after giving way to oncoming traffic, is becoming more widespread in the United States, particularly in Oregon, North Carolina, Michigan (replacing their trademark "red-ball" flashing left-turn lights), and Las Vegas, Nevada. In the normal sequence, a protected green left-turn arrow will first change to a solid yellow arrow to indicate the end of the protected phase, then to a flashing yellow arrow, which remains flashing until the standard green light changes to yellow and red. These generally take the form of four signal sections (green, yellow, yellow arrow, red). On some newer signals, notably in the city of Bend,{{where?|date=May 2015}} the green and flashing yellow arrows emanate from the same light section through the use of a dual-color LED array, while the solid yellow arrow is mounted above it. In Las Vegas, the arrow turns flashing yellow from a red light, before turning red again. | |||
=== Timing === | |||
Generally, a dedicated left-turn signal is illuminated at the beginning of the green phase of the green-yellow-red-green cycle. This is called a leading turn. This allows left-turn traffic, which often consists of just a few cars, to vacate the intersection quickly before giving priority to vehicles traveling straight. This increases the throughput of left-turn traffic while reducing the number of drivers, perhaps frustrated by long waits in heavy traffic for opposing traffic to clear, attempting to make an illegal left turn on red. A dedicated left-turn signal that appears at the end of the green phase is called a lagging turn. If there is no left-turn signal, the law requires one to yield to oncoming traffic and turn when the intersection is clear and it is safe to do so. Nevertheless, it is increasingly common in the U.S. to see drivers who do not yield in the absence of a dedicated signal, cutting off{{clarify|date=August 2014}} traffic that has the right-of-way and is starting to head across the intersection.{{Citation needed|date=July 2008}} In the U.S., many older inner-city and rural areas do not have dedicated left-turn lights, while most newer suburban areas have them. Such lights tend to decrease the overall efficiency of the intersection as it becomes congested, although it makes intersections safer by reducing the risk of head-on collisions and may even speed up through traffic, but if a significant amount of traffic is turning, a dedicated turn signal helps eliminate congestion. | |||
{{Main|Signal timing}} | |||
], Iran]] | |||
The timing of the intergreen is usually based on the size of the intersection, which can range from two to five seconds.{{Citation needed|date=February 2023}} Modelling programs include the ability to calculate intergreen times automatically. Intergreen periods are determined by calculating the path distance for every conflict point in the junction, which is the distance travelled to the conflict point by the movement losing right of way minus the distance travelled to the same conflict point by the movement gaining right of way using the possible conflict points (including with pedestrians) and calculating both the time it would take the last vehicle to clear the furthest collision point and the first vehicle from the next stage to arrive at the conflict point. At actuated junctions, integreens can be varied to account for traffic conditions.<ref name=":1" /> | |||
Engineers also need to set the amber timings (and red-amber, where appropriate), which is normally standardised by a traffic authority. For example, in the UK, the amber time is fixed nationally at three seconds and the red-amber time at two seconds, which results in a minimum intergreen time of five seconds (plus any all-red time).<ref name=":1" /> The US also uses a minimum of three seconds, but local traffic authorities can make timings longer, especially on wider, suburban roads. This variation has resulted in controversy when municipalities with shorter amber times use red light cameras.<ref>{{Cite web |title=Yellow lights shorter in Chicago |url=https://www.chicagotribune.com/news/ct-xpm-2010-03-22-ct-met-yellow-light-20100322-story.html |access-date=4 February 2023 |website=Chicago Tribune|date=22 March 2010 }}</ref> Where pedestrian signals are used, the timing of the "inivitation to cross" – the period where a steady walk signal shows – and clearance periods – time when the walk signal flashes or no signal is shown – need to be calculated. This is normally set against a design speed, e.g. {{Convert|1.2|m/s|ft/s|abbr=on}}. Similarly, these can be made extendable using sensors, allowing slower-moving pedestrians more time to cross the street.<ref name=":1" /> | |||
Some intersections with permissive turn signals occasionally have what is known as "]", "lag-trap", or "left turn trap" (in right-driving countries).{{Citation needed|date=December 2009}} This refers to situations when left-turning drivers are trapped in the intersection with a red light, while opposing traffic still has a green. In British Columbia, the law addresses this problem by giving a left-turning driver already in an intersection the right-of-way to make the turn once the intersection is otherwise clear, regardless of the traffic light state. | |||
=== Design guidance === | |||
For example, an intersection has dedicated left-turn signals for traffic traveling north. The southbound traffic gets a red light so northbound traffic can make a left turn, but the straight-through northbound traffic continues to get a green light. A southbound driver who had entered the intersection earlier will now be in a predicament, since they have no idea whether traffic continuing straight for both directions is becoming red, or just their direction. The driver will now have to check the traffic light behind them, which is often impossible from the viewing angle of a driver's seat. This can also happen when emergency vehicles or railroads preempt normal signal operation.<ref>{{cite web|url=http://midimagic@sgc-hosting.com/lagtrpqz.htm |title=Yellow Trap Quiz |accessdate=2013-04-02}}</ref> In the United States, signs reading "Oncoming traffic has extended green" or "Oncoming traffic may have extended green" must be posted at intersections where the "yellow trap" condition exists.<ref>{{cite web|url=http://mutcd.fhwa.dot.gov/htm/2003r1r2/part4/part4d.htm#section4D05 |title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4D |publisher=Mutcd.fhwa.dot.gov |accessdate=2009-05-19}}</ref><ref>{{cite web|url=http://mutcd.fhwa.dot.gov/htm/2003r1r2/part2/part2c.htm#section2C39 |title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 2C |publisher=Mutcd.fhwa.dot.gov |accessdate=2009-05-19}}</ref> | |||
National or sub-national highway authorities often issue guidance documents on the specification of traffic signals and design of signalised intersections according to national or local regulations. For example, in the United States the ] issues the ] and the ''Signalized Intersections Information Guide'', which is a synthesis of best practices and treatments to help practitioners make informed decisions.<ref>{{Cite web |title=Signalized Intersections Informational Guide |url=https://safety.fhwa.dot.gov/intersection/signal/fhwasa13027.pdf}}</ref> | |||
Although motorcycles and ] in most jurisdictions follow the same traffic signal rules for left turns as do cars and trucks, some places, such as ], have different rules. In these areas, it is not permitted for such small and often hard-to-see vehicles to turn left in front of oncoming traffic on certain high-volume roads when there is no dedicated left-turn signal. Instead, in order to make a left turn, the rider moves to the right side of the road, travels through the first half of the intersection on green, then slows down and stops directly in front of the line of cars on the driver's right waiting to travel across the intersection, which are of course being held by a red light. There is often a white box painted on the road in this location to indicate where the riders should group.{{Citation needed|date=December 2009}} The rider turns the bike 90 degrees to the left from the original direction of travel and proceeds along with the line of cars when the red light turns green, completing the left turn. This procedure improves safety because the rider never has to cross oncoming traffic, which is particularly important given the much greater likelihood of injury when a cycle is hit by a car or truck. This system (called a "]") is also used at many intersections in the CBD of Melbourne, Australia, where either or both streets carry tramways. This is done so right-turning vehicles (Australia drives on the left) do not block the passage of trams. The system is being extended to the suburbs. | |||
== |
== Variable lane control == | ||
{{Main|Lane control lights}} | {{Main|Lane control lights}} | ||
] typical lane control signal head]] | |||
], Canada]]Variable lane control is a form of intelligent transportation systems which involve the use of lane-use control signals, typically on a ] above a carriageway. These lights are used in ] systems to allow or forbid traffic to use one or more of the available lanes by the use of green lights or arrows (to permit) or by red lights or crosses (to prohibit).<ref name=":3">{{Cite web |title=FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4J |url=https://mutcd.fhwa.dot.gov/htm/2003r1/part4/part4j.htm |access-date=19 December 2021 |website=]}}</ref> Variable lane control may be in use at toll plazas to indicate open or closed booths; during heavy traffic to facilitate merging traffic from a slip road.<ref name=":3" /> | |||
In the US, most notably the Southeastern, there often is a "continuous-flow" lane. This lane is protected by a single, constant-green arrow pointing down at the lane(s) permitting the continuous flow of traffic, without regard to the condition of signals for other lanes or cross streets. Continuous lanes are restricted in that vehicles turning from a side street may not cross over the double white line to enter the continuous lane, and no lane changes are permitted to the continuous lane from an adjacent lane or from the continuous lane to an adjacent lane until the double white line has been passed. Some continuous lanes are protected by a raised curb located between the continuous lane and a normal traffic lane, with white and/or amber reflective paint or tape, prohibiting turning or adjacent traffic from entering the lane.{{cn|date=February 2024}} | |||
Lane-control lights are a specific type of traffic light used to manage traffic on a multi-way road, highway or tollway. Typically, these lights allow or forbid traffic to use one or more of the available lanes by the use of green lights or arrows (to permit) or by red lights or crosses (to prohibit). In the US, lane-control lights are often used to control and/or direct the flow of traffic through toll plazas and highway tunnels, such as during unusually-heavy traffic flow when more lanes may be required in one direction than in the other direction, or during a hurricane evacuation, when the lane signals for all lanes will show green for one direction to assist in more rapid traffic flow from the evacuation site. Lane-control lights are also used at highway weigh stations to direct tractor-trailers and other heavy or oversized vehicles into the proper lanes for weighing, inspection or exit. | |||
Continuous-flow traffic lanes are found only at "T" intersections where there is no side street or driveway entrance on the right side of the main thoroughfare; additionally, no pedestrians are permitted to cross the main thoroughfare at intersections with a continuous-flow lane, although crossing at the side street may be permitted. Intersections with continuous-flow lanes will be posted with a white regulatory sign approximately {{convert|500|feet|abbr=on}} before the intersection with the phrase, "right lane continuous traffic," or other, similar, wording. If the arrow is extinguished for any reason, whether by malfunction or design, traffic through the continuous lane will revert to the normal traffic pattern for adjacent lanes, except that turning or moving into or out of the restricted lane is still prohibited.{{cn|date=February 2024}} | |||
== |
== Waterways and railways == | ||
The three-aspect standard is also used at ]. Red means that another vessel is passing through. Amber means that the lock chamber is being emptied or filled to match the level of the approaching vessel. After the gate opens, green means that the vessel may enter. | |||
Traffic light failure in most jurisdictions in both drive-on-the-left Australia and some states of the mainly drive-on-the-right Europe must be handled by drivers as a priority-to-the-right intersection, or an all-way stop elsewhere, pending the arrival of a police officer to direct traffic. Some jurisdictions,{{which|date=December 2012}} however, have additional ] signs mounted above, below or next to the traffic lights; these take effect when the lights are no longer active. In the UK and parts of North America, drivers simply treat the junction as being uncontrolled when traffic lights fail, giving way as appropriate, unless a police officer is present. In much of the United States failed traffic signals must be treated as ] intersections. | |||
Railroad signals, for stopping trains in their own right of way, generally use the opposite positioning of the colours; that is, for signals above the driver's eyeline, green on top and red below is the ] of the signal colours on railroad tracks. There are three reasons for this variation: there is no risk that railway signals will be masked by a tall vehicle between the driver and the signal; train speeds in fog are much higher than for road vehicles, so it is important that the most restrictive signal is closest to the driver's eyeline; and with railway signals often in exposed rural locations, there is a risk of any signal other than the bottom one being masked by snow building up on the hood of the signal below. | |||
In ] as well as some jurisdictions in the US, traffic lights inactive at nighttime emit a yellow-colored flashing signal in directions owing priority while the intersecting street emit a flashing red light, requiring drivers to stop before proceeding. In Germany the priority directions will not be illuminated while the intersecting streets will be shown a flashing yellow signal. | |||
== |
== Rules == | ||
{{Main|Rules for traffic lights}} | |||
], United States]] | |||
] attempts to discourage red light running by posting the minimum fine.]]Traffic lights control flows of traffic using ] and legal rules. In most jurisdictions, it is against the law to disobey traffic signals and the police, or devices such as ]s, can issue fines or other penalties – and in some cases prosecute – drivers who break those laws.<ref>{{Cite web |date=8 April 2021 |title=Which European country has the strictest driving penalties? |url=https://zutobi.com/uk/driving-guides/driving-penalties-and-fines-in-eu |access-date=19 December 2021 |website=Zutobi Drivers Ed |language=en-GB}}</ref> US-based studies have found that the majority of drivers think that it is dangerous to run a red light at speed and the most common reason for red light running include inattentive driving, following an oversized vehicle or during inclement weather.<ref>{{Cite web |date=11 June 2020 |title=2019 Traffic Safety Culture Index |url=https://aaafoundation.org/2019-traffic-safety-culture-index/ |access-date=19 December 2021 |website=AAA Foundation |language=en-US}}</ref><ref>{{Cite web |date=25 March 2021 |title=How to Prevent Red Light Runners |url=https://www.westernsystems-inc.com/stop-red-light-running/ |access-date=19 December 2021 |website=Western Systems |language=en-US}}</ref> | |||
In an era when intersections were often controlled by a single traffic signal head, many signals were installed on pedestals in the centers of intersections. Often referred to as "dummy lights," these installations often replaced beacons or "mushrooms" that denoted the centers of intersections and separated opposing traffic, with the infrastructure used for the beacons and mushrooms serving the new "stop and go" type signals. | |||
The rules governing traffic light junctions for vehicles differ by jurisdiction. For example, it is common in ] that drivers can turn kerb-to-kerb (i.e. turning right at most junctions), even when a red light shows.<ref>{{cite news |author=Michael Knight |date=30 December 1979 |title=For Boston Drivers It's Turn Right on Red and Full Speed Ahead |work=The New York Times |url=https://www.nytimes.com/1979/12/30/archives/for-boston-drivers-its-turn-right-on-red-and-full-speed-ahead.html |access-date=11 August 2022}}</ref><ref>{{UnitedStatesCode|42|6322}}</ref> On the other hand, this ] rule is uncommon in Europe, unless an arrow signal or traffic sign specifically permits it.<ref>{{cite web |title=The Green Arrow |url=http://www.gruenpfeil.de/in-english.html |access-date=28 January 2021 |website=German Pedestrians' Association (FUSS e.V.) |archive-date=28 January 2021 |archive-url=https://web.archive.org/web/20210128024359/http://gruenpfeil.de/in-english.html |url-status=dead }}</ref><ref>{{cite journal |date=2016 |title=Pravilnik o prometni signalizaciji in prometni opremi na javnih cestah |url=http://www.pisrs.si/Pis.web/npbDocPdf?idPredpisa=PRAV13786&idPredpisaChng=PRAV11505&type=pdf |journal=Uradni List RS |language=sl |publisher=Služba Vlade RS za zakonodajo |page=56 |access-date=25 August 2021 |quote=2444 — Vožnja desno ob rdeči luči na semaforju}}</ref><ref>Arrêté du 24 novembre 1967 relatif à la signalisation des routes et des autoroutes – Article 7. {{cite web |title=Arrêté du 24 novembre 1967 relatif à la signalisation des routes et des autoroutes – Article 7 | Legifrance |url=http://www.legifrance.gouv.fr/affichTexteArticle.do;jsessionid=8EE36C429C78C3EFCB06EDB0F10FDA60.tpdila10v_2?idArticle%3DLEGIARTI000025705490%26cidTexte%3DJORFTEXT000000829916%26categorieLien%3Did%26dateTexte%3D |url-status=live |archive-url=https://web.archive.org/web/20160412185700/https://www.legifrance.gouv.fr/affichTexteArticle.do%3Bjsessionid%3D8EE36C429C78C3EFCB06EDB0F10FDA60.tpdila10v_2?idArticle=LEGIARTI000025705490&cidTexte=JORFTEXT000000829916&categorieLien=id&dateTexte= |archive-date=12 April 2016 |access-date=2 October 2015}}</ref><ref>{{cite web |title=The Highway Code: Using the road (rule 177) |url=https://www.gov.uk/using-the-road-159-to-203/road-junctions-170-to-183 |access-date=26 June 2015}}</ref> | |||
There are a handful of operational dummy lights still in service. Three are located in ]: ], ] and ].<ref>File:Croton-on-Hudson Dummy Light.jpg</ref> | |||
== Design == | |||
After a dummy light was knocked down by a truck in 2010, the city of Coleman, Texas decided to preserve and refurbish its last two pedestal mounted dummy lights as part of its historic district preservation efforts. | |||
=== Bulbs === | |||
In 2011, the Arkansas ] nominated the state's last remaining pedestal mounted signal, located in ], to be listed on the ].{{citation needed|date=August 2014}} | |||
Conventional traffic signal lighting, still common in some areas, uses a standard light bulb. The light then bounces off a mirrored glass or polished aluminium reflector bowl, and out through a polycarbonate plastic or glass signal lens. In some signals, these lenses were cut to include a specific refracting pattern. Traditionally, incandescent and halogen bulbs were used. Because of the low efficiency of light output and a single point of failure (filament burnout), some traffic authorities are choosing to retrofit traffic signals with ] arrays that consume less power, have increased light output, and last significantly longer.{{Citation needed|date=July 2020}} Moreover, in the event of an individual LED failure, the aspect will still operate albeit with a reduced light output. The light pattern of an LED array can be comparable to the pattern of an incandescent or halogen bulb fitted with a ]. | |||
The low energy consumption of LED lights can pose a driving risk in some areas during winter. Unlike incandescent and halogen bulbs, which generally get hot enough to melt away any snow that may settle on individual lights, LED displays – using only a fraction of the energy – remain too cool for this to happen.<ref>{{cite web |url=http://www.ctv.ca/CTVNews/Canada/20100110/LED_Snow_100110/ |title=LED traffic lights could pose winter driving risk |publisher=CTV |date=5 October 2011 |access-date=5 October 2011}}{{dead link|date=July 2021|bot=medic}}{{cbignore|bot=medic}}</ref><ref>{{cite web|url=https://abcnews.go.com/GMA/ConsumerNews/led-traffic-lights-unusual-potentially-deadly-winter-problem/story?id=9506449|title=LED Traffic Lights Unusual, Potentially Deadly Winter Problem |author=Elizabeth Leamy |author2=Vanessa Weber |date=4 January 2010 |work=ABC News}}</ref> As a response to the safety concerns, a heating element on the lens was developed.<ref>{{cite web |author=Marmarelli, Beth |title=Engineering Team Develops Device to Aid LED Traffic Signals in Inclement Weather & Places Overall in Campus's Senior Design Competition |publisher=University of Michigan |date=22 June 2011 |url=http://sustainability.umich.edu/news/engineering-team-develops-device-aid-led-traffic-signals-inclement-weather-places-overall-campu |access-date=22 June 2011 |archive-date=13 April 2012 |archive-url=https://web.archive.org/web/20120413011756/http://sustainability.umich.edu/news/engineering-team-develops-device-aid-led-traffic-signals-inclement-weather-places-overall-campu |url-status=dead }}</ref><ref>{{cite web |url=http://www.faqs.org/patents/app/20120255942 |publisher=United States Patent Office |title=Patent application title: Traffic Light Heater |work=Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942 |author=Hankscraft Inc. |date=11 October 2012 | access-date=11 October 2012}}</ref> | |||
The oldest working 'dummy' style beacon in Rhode Island was located in the Historic Mill village of Albion in the Blackstone River Valley (Town of Lincoln RI). It was erected in 1932 above where the old village well stood in the center square. In April 2015 it was destroyed by a motorist. The beacon was a local historical site and the logo for a local Boy Scout Troop, Troop 711 Albion. | |||
Increases in traffic flows have prompted calls for these types of traffic lights to be removed due to safety concerns, but their historic value has kept these landmarks at their original locations. To serve historic district applications, Teeco Safety Systems of ], still manufactures replacement fixed 4-way traffic signals for pedestal and overhead span wire installations.{{Citation needed|date=December 2009}} | |||
== Technology == | |||
=== Optics and lighting === | |||
] | |||
Traditionally, incandescent and halogen bulbs were used. Because of the low efficiency of light output and a single point of failure (filament burnout) municipalities are increasingly retrofitting traffic signals with ] arrays that consume less power, have increased light output, last significantly longer, and in the event of an individual LED failure, still operate albeit with a reduced light output. With the use of optics, the light pattern of an LED array can be comparable to the pattern of an incandescent or halogen bulb. | |||
The low energy consumption of LED lights can pose a driving risk in some areas during winter. Unlike incandescent and halogen bulbs, which generally get hot enough to melt away any snow that may settle on individual lights, LED displays – using only a fraction of the energy – remain too cool for this to happen.<ref>{{cite web |url=http://www.ctv.ca/CTVNews/Canada/20100110/LED_Snow_100110/ |title=LED traffic lights could pose winter driving risk |publisher=CTV |date=5 October 2011 |accessdate=5 October 2011}}</ref><ref>{{cite web|url=http://abcnews.go.com/GMA/ConsumerNews/led-traffic-lights-unusual-potentially-deadly-winter-problem/story?id=9506449|title=LED Traffic Lights Unusual, Potentially Deadly Winter Problem - ABC News|author=ABC News|work=ABC News}}</ref> As a response to the safety concerns, a heating element on the lens was developed. <ref>{{cite web |url=http://sustainability.umich.edu/news/engineering-team-develops-device-aid-led-traffic-signals-inclement-weather-places-overall-campu |author=Marmarelli, Beth |title=Engineering Team Develops Device to Aid LED Traffic Signals in Inclement Weather & Places Overall in Campus's Senior Design Competition |publisher=University of Michigan |date=22 June 2011 |accessdate=22 June 2011}}</ref><ref>{{cite web|url=http://www.faqs.org/patents/app/20120255942 |publisher=United States Patent Office |title=Patent application title: Traffic Light Heater |work=Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942 |author=Hankscraft Inc. |date=11 October 2012 | accessdate=11 October 2012}}</ref> | |||
=== Programmable visibility signals === | === Programmable visibility signals === | ||
{{Multiple image | |||
| align = right | |||
| direction = vertical | |||
| width = 300 | |||
| image1 = First and Mill 3Ms img14.jpg{{!}}3M traffic signals in Shelton, Washington, as seen off-axis from the intended viewing area. These signals appear to be "off" or invisible to adjacent lanes of traffic during the daytime. Only a faint glow can be seen when viewed at night. | |||
| image2 = First and Mill 3Ms img07.jpg{{!}}3M traffic signals in Shelton, Washington, as seen from the signal's intended viewing area. Special light-diffusing optics and a coloured Fresnel lens create the indication | |||
| footer = Traffic signals installed in ], seen off-axis from the intended viewing area (''top'') and from the signal's intended viewing area (''bottom'').{{pb}}From off-axis, these signals appear to be "off" or invisible to adjacent lanes of traffic during the daytime. Only a faint glow can be seen when viewed at night. | |||
}} | |||
Signals such as the 3M High Visibility Signal utilize light-diffusing optics and a ] to create the signal indication. The light from a 150 W PAR46 sealed-beam lamp in these "programmable visibility" signals passes through a set of two glass lenses at the back of the signal. The first lens, a frosted glass diffusing lens, diffuses the light into a uniform ball of light around five inches in diameter. The light then passes through a nearly identical lens known as an optical limiter (3M's definition of the lens itself), also known as a "programming lens", also five inches in diameter.{{Citation needed|date=July 2020}} | |||
], Nova Scotia, with specially-shaped lights to assist people with color blindness]] | |||
Using a special aluminium foil-based adhesive tape, these signals are "masked" or programmed by the programming lens so that only certain lanes of traffic will view the indication. At the front of these programmable visibility signals is a 12" Fresnel lens, each lens tinted to meet United States ] (ITE) chromaticity and luminance standards. The Fresnel lens collimates the light output created by the lamp and creates a uniform display of light for the lane in which it is intended. | |||
]. Standing off-axis from the intended viewing area, these signals appear to be "off" or invisible to adjacent lanes of traffic during the daytime. Only a faint glow can be seen when viewed at night]] | |||
In addition to being positioned and mounted for desired visibility for their respective traffic, some traffic lights are also aimed, louvered, or shaded to minimize misinterpretation from other lanes. For example, a Fresnel lens on an adjacent through-lane signal may be aimed to prevent left-turning traffic from anticipating its own green arrow. Intelight Inc. manufactures a programmable traffic signal that uses a software-controlled LED array and electronics to steer the light beam toward the desired approach.<ref>{{cite web|url=http://intelight-its.com/product/esb-signals/item/34-intelight-esb-traffic-signal-head.html|title=Intelight ESB Traffic Signal Head|work=intelight-its.com|access-date=21 June 2013|archive-url=https://web.archive.org/web/20140808220251/http://intelight-its.com/product/esb-signals/item/34-intelight-esb-traffic-signal-head.html|archive-date=8 August 2014|url-status=dead}}</ref> The signal is programmed unlike the 3M and McCain models. It requires a connection to a laptop or smartphone with the manufacturer's software installed. Connections can be made directly with a direct-serial interface kit, or wirelessly with a radio kit over WIFI to the signal. In addition to aiming, Fresnel lenses, and louvers, visors and back panels are also useful in areas where sunlight would diminish the contrast and visibility of a signal face. Typical applications for these signals were skewed intersections, specific multi-lane control, left-turn pocket signals, or other areas where complex traffic situations existed. | |||
]Signals such as the ] and McCain Programmable Visibility signal utilize light-diffusing optics and a Fresnel lens to create the signal indication. Lit via a powerful 150W PAR46 sealed-beam lamp, the light from the lamp in these "programmable visibility" signals passes through a set of two glass lenses at the back of the signal. The first lens, a frosted glass diffusing lens, diffuses the light into a uniform ball of light around five inches in diameter. The light then passes through a nearly identical lens known as an optical limiter (3M's definition of the lens itself), also known as a "programming lens", also five inches in diameter. | |||
] | |||
Using a special aluminum foil-based adhesive tape, these signals are "masked" or programmed via the programming lens so that only certain lanes of traffic will view the indication. At the front of these programmable visibility signals is a 12" Fresnel lens, each lens tinted to meet United States ] (ITE) chromaticity and luminance standards. The Fresnel lens collimates the light output created by the lamp, and creates a uniform display of light for the lane in which it is intended. These signals were first developed by the ] Company in the late 1960s,{{Citation needed|date=December 2009}} and were popular in the late 1970s as traffic density increased. | |||
=== Size === | |||
In addition to being positioned and mounted for desired visibility for their respective traffic, some traffic lights are also aimed, louvered, or shaded to minimize mis-interpretation from other lanes. For example, a ] on an adjacent through-lane signal may be aimed to prevent left-turning traffic from anticipating its own green arrow. One example of the Fresnel lens application common in the U.S. is the ] (dubbed the "Programmed Visibility" signal). | |||
In the United States, traffic lights are currently designed with lights approximately {{convert|12|in|-1}} in diameter. Previously the standard had been {{convert|8|in|-1}}; however, those are slowly being phased out in favour of the larger and more visible 12 inch lights. Variations used have also included a hybrid design, which had one or more 12 inch lights along with one or more lights of {{convert|8|in|-1}} on the same light. | |||
In the United Kingdom, 12-inch lights were implemented only with Mellor Design Signal heads designed by ]. These were designed for symbolic optics to compensate for the light loss caused by the symbol. However, following a study sponsored by the UK Highways Agency and completed by Aston University, Birmingham, UK, an enhanced optical design was introduced in the mid-1990s. Criticism{{by whom|date=February 2024}} of sunlight ''washout'' (cannot see the illuminated signal due to sunlight falling on it), and ''sun-phantom'' (signal appearing to be illuminated even when not due to sunlight reflecting from the parabolic mirror at low sun angles), led to the design of a signal that used lenslets to focus light from a traditional incandescent bulb through apertures in a matt black front mask. This cured both problems in an easily manufactured solution. This design proved successful and was taken into production by a number of traffic signal manufacturers through the engineering designs of Dr. Mark Aston, working firstly at the SIRA Ltd in Kent, and latterly as an independent optical designer.{{Citation needed|date=December 2008}} | |||
Today, McCain Traffic Systems is the only U.S.-based manufacturer producing optically programmable traffic signals similar to the 3M model. Intelight Inc. manufactures a programmable traffic signal that uses a software-controlled LED array and electronics to steer the light beam toward the desired approach.<ref>{{cite web|url=http://intelight-its.com/product/esb-signals/item/34-intelight-esb-traffic-signal-head.html|title=Intelight ESB Traffic Signal Head|work=intelight-its.com}}</ref> The signal is programmed unlike the 3M and McCain models. It requires a connection to a laptop or smartphone with the manufacturer software installed. Connections can be made directly with a direct-serial interface kit, or wirelessly with a radio kit over WIFI to the signal. | |||
In addition to aiming, Fresnel lenses, and louvers, visors and back panels are also useful in areas where sunlight would diminish the contrast and visibility of a signal face. | |||
Typical applications for these signals were skewed intersections, specific multi-lane control, left-turn pocket signals or other areas where complex traffic situations existed. | |||
=== Conventional lighting systems === | |||
Conventional traffic signal lighting, still common in some areas, utilizes a standard light bulb. Typically, a 67, 69, or 115 watt medium-base (household lamp in the US) light bulb provides the illumination.{{Citation needed|date=December 2009}} Light then bounces off a mirrored glass or polished aluminium reflector bowl, and out through a polycarbonate plastic or glass signal lens. In some signals, these lenses were cut to include a specific refracting pattern. Crouse-Hinds is one notable company for this practice. In the 1930s throughout the 1950s, they utilized a beaded prismatic lens with a "smiley" pattern embossed into the bottom of each lens.{{Citation needed|date=December 2009}} | |||
=== Light design === | |||
In the United States, traffic lights are currently designed with lights approximately {{convert|12|in|-1|-1}} in diameter. Previously the standard had been {{convert|8|in|-1|-1}}, however those are slowly being phased out in favor of the larger and more visible 12 inch lights. Variations used have also included a hybrid design, which had one or more 12 inch lights along with one or more lights of {{convert|8|in|-1|-1}} on the same light. For example, these "12-8-8" (along with 8-8-8) lights are standard in most jurisdictions in Ontario, Manitoba, and British Columbia (that, is, the red light is 12 and others 8, making the red more prominent). {{Citation needed|date=December 2008}} | |||
In the United Kingdom, 12 inch lights were implemented only with Mellor Design Signal heads designed by ]. These were designed for symbolic optics to compensate for the light loss caused by the symbol. With the invention of anti-phantom, highly visible SIRA lenses, lights of {{convert|8|in|mm|-1|-1}} could be designed to give the same output as plain lenses, so a larger surface area was unnecessary. Consequently lights of {{convert|12|in|-1|-1}} are no longer approved for use in the UK and all lights installed on new installations have to be {{convert|200|mm|0|0|abbr=on}} in accordance with TSRGD (Traffic Signs Regulations and General Directions). Exemptions are made for temporary or replacement signals. {{Citation needed|date=December 2008}} | |||
=== Technological advancements === | |||
With technologies in developed countries continuing to advance, there is now an increasing move{{by whom|date=August 2014}} to develop and implement ]s on the roads.{{where|date=August 2014}} These are systems that adapt to information that is received from a central computer about the position, speed and direction of vehicles. They try to communicate with cars to alert drivers of impending light changes and reduce motorists' waiting time considerably.{{clarify|date=August 2014}} Trials are currently being conducted for the implementation of these advanced traffic lights but there are still many hurdles to widespread use that need to be addressed; one of which is the fact that few cars yet have the required systems to communicate with these lights. | |||
=== Control and coordination === | |||
{{Main|Traffic light control and coordination}} | |||
The manufacturers took a licence for the generic design from the Highways Agency, with Dr. Aston engineering a unique solution for each manufacturer. Producing both bulb and LED versions of the signal aspects, these signals are still the most common type of traffic light on UK roads. With the invention of anti-phantom, highly visible Aston lenses, lights of {{convert|8|in|mm|-1}} could be designed to give the same output as plain lenses, so a larger surface area was unnecessary. Consequently, lights of {{convert|12|in|-1}} are no longer approved for use in the UK and all lights installed on new installations have to be {{convert|200|mm|0|abbr=on}} in accordance with TSRGD (Traffic Signs Regulations and General Directions). Exemptions are made for temporary or replacement signals.{{Citation needed|date=December 2008}} | |||
The normal function of traffic lights requires sophisticated control and coordination to ensure that traffic moves as smoothly and safely as possible and that pedestrians are protected when they cross the roads. | |||
=== Mounting === | === Mounting and placement === | ||
<gallery mode="nolines" widths="160"> | |||
There are significant differences from place to place in how traffic lights are mounted or positioned so that they are visible to drivers. Depending upon the location, traffic lights may be mounted on poles situated on street corners, hung from horizontal poles or wires strung over the roadway, or installed within large horizontal gantries that extend out from the corner and over the right-of-way. In the last case, such poles or gantries often have a lit sign with the name of the cross-street. | |||
File:Part time traffic lights on the Pialligo Avenue.jpg|Part time pole/pedestal-mounted traffic lights in ], Australia | |||
<gallery mode="packed"> | |||
File:Traffic lights and vehicular transportation in Ekiti State. 05.jpg|Mast-arm traffic lights in ], Nigeria | |||
File:Taiyuan Road shops and pedestrian overpass 20100622.jpg|Horizontal traffic lights mounted on a footbridge in ], Taiwan | |||
9th-food.jpg|A typical traffic light on ] in ] Note that the traffic light gantry is of a guy-wire masted style, which is unique to New York City. | |||
File:Dummy Light.jpg|A dummy light in ], New York. It was removed in 2021.<ref name="RECORDER"> {{Webarchive|url=https://web.archive.org/web/20230710165750/https://www.recordernews.com/news/local-news/203892 |date=10 July 2023 }}, Retrieved Jul. 10, 2023.</ref> | |||
Joy Street Portal location.JPG|A vertically mounted traffic light in ], Massachusetts, with pole-mounted traffic light in the foreground. | |||
2014-12-20 14 49 17 Horizontally-mounted traffic light at the intersection of Calhoun Street (Mercer County Route 653) and Spring Street in Trenton, New Jersey.JPG|Example of horizontally mounted traffic light in ], ]. | |||
Traffic light at megasection.jpg|An imposing tubular metal structure. The intersection is not only very large, but due to its location near the Florida east coast must be hurricane resistant. | |||
</gallery> | </gallery> | ||
The MUTCD identifies five types of traffic light mounts. On pedestals, signal heads are mounted on a single pole (this is the normal installation method for the UK).<ref name=":9">{{Cite book |last=Buckholz |first=Jeffrey W. |url=https://www.cedengineering.com/userfiles/Traffic%20Signal%20Supports%20-R1.pdf |title=Traffic Signal Supports, Indications and Signing |publisher=CED Engineering |location=Woodcliff Lake, NJ}}</ref><ref name=":1" /> On mast arms, signal heads are mounted on a rigid arm over the road protuding from the pole. On strained poles, signals are suspended over a roadway on a wire, attached to poles at opposite kerbs. This is the most common installation method in the United States. Unipoles are similar to strain poles, but a single structure over the road, rather than two poles linked with wire. Finally, signals can be attached to existing structures such as an overpass.<ref name=":9" /> Dummy lights are traffic signs located in the centre of a junction, which operate on a fixed cycle. These have generally been decommissioned due to safety concerns; however, a number remain due to historic value.<ref>{{Cite web |title=A Dummy Forever! |url=https://www.crotonfriendsofhistory.org/dummy-forever |access-date=18 December 2021 |website=Croton Friends of History |language=en-US}}</ref> | |||
In some locations, lights are mounted with their multiple faces arranged horizontally, often with supplemental vertical signals on the side, while others locations use vertical signals almost exclusively. Horizontal signals have consistent orientation, like their vertical counterparts.<ref>{{cite web|url=http://mutcd.fhwa.dot.gov/HTM/2003r1/part4/fig4d-03_longdesc.htm |title=FHWA– MUTCD– 2003 Edition Revision 1 Fig. 4D-3 Long Description |publisher=Mutcd.fhwa.dot.gov |accessdate=2009-05-19}}</ref> Often, supplemental curb pedestal mounts, intended to support a signal for a different approach road, are used when primary signals are partially obscured due to structures such as overpasses, approaches around a building that obscure the primary signal mountings, and unusual approach geometry. In Florida, horizontal signals mounted on poles, known as "mast arms", are in wide use due to their lower wind profile, important for minimizing ] damage. In areas where wind-load is not as much of a concern as ice-load, such as ] or ], the lights are mounted vertically to reduce the accumulation of ice or snow over the surface of the signal heads. In a few countries such as ], ], ] and a few jurisdictions in Canada and the US such as ], ], ], ], and ], most traffic signals are mounted horizontally. | |||
Signals can either be placed nearside – between the stop line and the kerbline of the intersecting road – or farside – on the opposite side of the junction. In European countries, signals are often placed on the nearside.<ref name=":10">{{Cite web |date=30 April 2021 |title=Near Side Signals: Thinking Outside the Pedestrian Box |url=https://streets.mn/2021/04/30/thinking-outside-the-pedestrian-box/ |access-date=4 February 2023 |website=Streets.mn |language=en-US}}</ref> In the UK, at least two signal heads are required (known as the primary and secondary heads), one of which is normally nearside and the other of which could be nearside or farside.<ref name=":1" /> In the US, signals are normally located farside, though in some states, nearside signals are also used. Nearside signals can be beneficial to road safety, as drivers have more time to see a red light and are less likely to encroach on pedestrian crossings.<ref name=":10" /> | |||
Traffic signals in most areas of Europe are located at the stop line on same side of the intersection as the approaching traffic (there being both ]) and are often mounted overhead as well as on side of the road. At particularly busy junctions for freight, higher lights may be mounted specifically for ]. The stop line alignment is done to prevent vehicles blocking any crosswalk and allow for better pedestrian traffic flow. There may also be a special area a few meters in advance of the stop line where cyclists may legally wait but not motor vehicles; this ] is often painted with a different road surface with greater friction and a high color, both for the benefit of cyclists and for other vehicles. The traffic lights are mounted so that cyclists can still see them. | |||
== Effects == | |||
In Spain, the mounted traffic lights on the far side of the intersection is meant for the traffic that exits the intersection in that particular direction. This is often done due to the pedestrian crossings, so that traffic has to wait if they get a red light. These intersections also come with a stop line in the exit area of the intersection. | |||
Drivers spend on average around 2% of journey time passing through signalised junctions.<ref name=":4">{{Cite web|title=Why traffic lights are pollution hotspots|url=https://www.weforum.org/agenda/2015/02/why-traffic-lights-are-pollution-hotspots/|access-date=19 December 2021|website=World Economic Forum|language=en}}</ref> Traffic lights can increase the traffic capacity at intersections and reduce delay for side road traffic, but can also result in increased delay for main road traffic.<ref>{{cite web|date=September 2007|title=Traffic Signals|url=http://www.ite.org/safety/issuebriefs/Traffic%20Signals%20Issue%20Brief.pdf|url-status=dead|archive-url=https://web.archive.org/web/20090327022232/http://www.ite.org/safety/issuebriefs/Traffic%20Signals%20Issue%20Brief.pdf|archive-date=27 March 2009|access-date=1 April 2009|publisher=Institute of Transportation Engineers}}</ref> ], the innovative Dutch traffic engineer, and pioneer of ] schemes, was sceptical of their role, and is quoted as having said of them: "We only want traffic lights where they are useful and I haven't found anywhere where they are useful yet."<ref>{{cite news|author=David Millward|date=4 November 2006|title=Is this the end of the road for traffic lights?|work=The Daily Telegraph|url=https://www.telegraph.co.uk/news/uknews/1533248/Is-this-the-end-of-the-road-for-traffic-lights.html|access-date=1 April 2009}}</ref> | |||
A World Economic Forum study found that signalised junctions are linked to higher rates of localised air pollution. Drivers accelerate and stop frequently at lights and as such peak particle concentration can be around 29 times higher than during free-flow conditions. The WEF recommends that traffic authorities synchronise traffic signals, consider alternative traffic management systems and consider placing traffic lights away from residential areas, schools, and hospitals.<ref name=":4" /> | |||
In North America, there is often a pole-mounted signal on the same side of the intersection, but additional pole-mounted and overhead signals are usually mounted on the far side of the intersection for better visibility. Most traffic lights are mounted that way in the Western United States and Canada. | |||
The separation of conflicting streams of traffic in time can reduce the chances of right-angle collisions by turning traffic and cross traffic, but they can increase the frequency of rear-end crashes by up to 50%.<ref name="CRF">National Cooperative Highway Research Program, Crash Reduction Factors for Traffic Engineering and Intelligent Transportation System (ITS) Improvements: State-of-Knowledge Report, November 2005, Table 3</ref> Since right-angled and turn-against-traffic collisions are more likely to result in injuries, this is often an acceptable trade-off. They can also adversely affect the safety of bicycle and pedestrian traffic. Between 1979 and 1988, the city of ], Pennsylvania, removed signals at 199 intersections that were not warranted. On average, the intersections had 24% fewer crashes after the unwarranted signals were removed.<ref name="CRF" /> The traffic lights had been erected in the 1960s because of since-resolved protests over traffic. By 1992, over 800 traffic lights had been removed at 426 intersections, and the number of crashes at these intersections dropped by 60%.<ref>{{cite web|url=http://articles.philly.com/1992-04-19/news/26003417_1_traffic-signals-traffic-lights-slow-traffic|archive-url=https://web.archive.org/web/20150404015508/http://articles.philly.com/1992-04-19/news/26003417_1_traffic-signals-traffic-lights-slow-traffic|url-status=dead|archive-date=4 April 2015|title=Archives - Philly.com|website=]}}</ref> | |||
In some areas of the United States, signals facing in up to four directions are hung directly over the intersection on a wire strung diagonally over the intersection (once common in ]), or the signal faces traffic in one direction, still hung by wires (but the wire is strung horizontally between two adjacent corners of the intersection). This is common in the Southern and Eastern United States. | |||
== Justification == | |||
In other countries like Australia, New Zealand, UK, traffic lights are mounted at the stop line before the intersection and also after the intersection. Some busy intersections have an overhead traffic light for heavy vehicles and vehicles further away. | |||
{{Globalize section|USA|2name=the United States|date=December 2010}} | |||
Criteria have been developed to help ensure that new traffic lights are installed only where they will do more good than harm and to justify the removal of existing traffic lights where they are not warranted. They are most often placed on arterial roads at intersections with either another arterial road or a collector road, or on an expressway where an interchange is not warranted. In some situations, traffic signals can also be found on collector roads in busy settings. | |||
The ] provides input as to standards concerning traffic signals and control devices. One example is the input the association provided for the ] (MUTCD).<ref>{{Citation |title=International Municipal Signal Association |date=23 October 2021 |url=https://en.wikipedia.org/search/?title=International_Municipal_Signal_Association&oldid=1051364245 |work=Misplaced Pages |access-date=8 July 2023 |language=en}}</ref> The MUTCD is issued by the ] (FHWA) of the ] (USDOT).<ref>{{Citation |title=Manual on Uniform Traffic Control Devices |date=8 July 2023 |url=https://en.wikipedia.org/search/?title=Manual_on_Uniform_Traffic_Control_Devices&oldid=1164284829 |work=Misplaced Pages |access-date=8 July 2023 |language=en}}</ref> | |||
== Implementation == | |||
According to transportation engineers, traffic lights can have both positive and negative effects on traffic safety and traffic flow. The separation of conflicting streams of traffic in time can reduce the chances of right-angle collisions. But also the frequency of rear-end crashes can be increased by the installation of traffic lights, and they can adversely affect the safety of bicycle and pedestrian traffic. They can increase the traffic capacity at intersections, but can also result in excessive traffic delay.<ref>{{cite web |title=Traffic Signals |publisher=Institute of Transportation Engineers |date=September 2007 |url=http://www.ite.org/safety/issuebriefs/Traffic%20Signals%20Issue%20Brief.pdf |accessdate=2009-04-01}}</ref> ], the innovative Dutch traffic engineer, and pioneer of ] schemes, was sceptical of their role, and is quoted as having said of them: "We only want traffic lights where they are useful and I haven't found anywhere where they are useful yet."<ref>{{cite news | |||
| title=Is this the end of the road for traffic lights? | |||
| author=David Millward | |||
| date=4 November 2006 | |||
| work=The Daily Telegraph | |||
| url=http://www.telegraph.co.uk/news/uknews/1533248/Is-this-the-end-of-the-road-for-traffic-lights.html | |||
| accessdate=2009-04-01 | |||
}}</ref> | |||
In the United States, the criteria for installation of a traffic control signal are prescribed by the ] (MUTCD), which defines the criteria in nine ''warrants'':<ref>. Mutcd.fhwa.dot.gov.</ref> | |||
=== Small vehicle safety === | |||
* Eight-hour vehicular volume. Traffic volume must exceed prescribed minima for eight hours of an average weekday. | |||
In some instances the stoplight traffic detector will not change the light for small vehicles such as motorcycles, scooters and particularly bicycles, because the ] sensor fails to detect the small vehicle. A vehicle with sufficient mass of metal such as steel interacts with the sensor's magnetic field causing the light to change at the appropriate time.<ref>. Auto.howstuffworks.com (1 April 2000).</ref> Motorcycles and scooters have much less mass than cars, resulting in a failure to trigger the sensor, while bicycles may not even be constructed with metal. This situation most often occurs at the times of day when other traffic is sparse as well as when the small vehicle is coming from a direction that does not have a high volume of traffic.<ref>. Motorcycleassistant.com.</ref> Not all sensor traffic lights have this problem. There are some that can pick up these vehicles without problems and most are capable of doing so. However, through road construction and other processes, they are not properly adjusted or calibrated for the small vehicles. ] detect vehicles passing over them and not necessarily stationary vehicles. | |||
* Four-hour vehicular volume. Traffic volume must exceed prescribed minima for four hours of an average weekday. | |||
* Peak hour volume or delay. This is applied only in unusual cases, such as ]s, industrial complexes, and ] lots that attract or discharge large numbers of vehicles in a short time, and for a minimum of one hour of an average weekday. The side road traffic suffers undue delays when entering or crossing the major street. | |||
'''Actuated traffic lights''' | |||
Some states in the United States have passed laws which give motorcyclists an affirmative defense to proceed through a red light with caution after stopping when the device which causes the light to change from red to green does not activate.<ref>{{cite web|url=http://www.usatoday.com/news/nation/2008-06-10-red-light-laws_N.htm|title=States green-light new red-light laws for motorcycles|author=Ron Barnett|work=USA Today|publisher=Gannett Co. Inc.|date=6 June 2008|accessdate=11 May 2011}}</ref> A partial listing of these state statutes include , , , , North Carolina, Idaho, Arkansas, and Tennessee. Additional state laws regarding actuated traffic lights can be found at the , including this . | |||
=== Traffic signal warrants === | |||
{{Globalize/US|date=December 2010}} | |||
Traffic signals have strengths and weaknesses that must be considered when deciding whether to install them. Signaled intersections can reduce delay for side road traffic and reduce the occurrence of collisions by turning traffic and cross traffic. But they may also cause delay for traffic on the main road, and often increase ]s by up to 50%.<ref name=CRF>National Cooperative Highway Research Program, Crash Reduction Factors for Traffic Engineering and Intelligent Transportation System (ITS) Improvements: State-of-Knowledge Report, November 2005, Table 3</ref> Since right-angled and turn-against-traffic collisions are more likely to result in injuries, this is often an acceptable trade-off. | |||
== United States MUTCD == | |||
Criteria have been developed to help ensure that new signals are installed only where they will do more good than harm. In the United States these criteria are called ''warrants'', and are found in the ] (MUTCD), the Federal regulation covering the use of signs, pavement markings, traffic signals, and similar devices. | |||
In the US MUTCD, there are nine warrants for traffic signals:<ref>. Mutcd.fhwa.dot.gov.</ref> | |||
* Eight-hour vehicular volume. Traffic volume must exceed prescribed minima for eight hours of an average day (usually a weekday). | |||
<!-- {{Clarify|reason=Does weekday include Saturday?|date=March 2009}} | |||
The MUTCD text specifies "average day", except in Warrant 8, where it mentions the term "weekday". But the MUTCD usage of "weekday" does not include Saturday or Sunday, because Warrant 8 specifies different conditions for Saturday and Sunday. Refer to Section 4C.09 for this usage, there's a citation link now. --> | |||
* Four-hour vehicular volume. Traffic volume must exceed prescribed minima for four hours of an average day. | |||
* Peak hour volume or delay. This is applied only in unusual cases, such as ]s, industrial complexes, and ] lots that attract or discharge large numbers of vehicles in a short time, and, for a minimum of one hour of an average day. The side road traffic suffers undue delays when entering or crossing the major street. | |||
* Pedestrian volume. If the traffic volume on a major street is so heavy that pedestrians experience excessive delays in attempting to cross it. | * Pedestrian volume. If the traffic volume on a major street is so heavy that pedestrians experience excessive delays in attempting to cross it. | ||
* School crossing. If the traffic density at school crossing times exceeds one per minute which is considered to provide too few gaps in the traffic for children to safely cross the street. | * School crossing. If the traffic density at school crossing times exceeds one per minute which is considered to provide too few gaps in the traffic for children to safely cross the street. | ||
Line 346: | Line 433: | ||
* Intersection near a grade crossing. A traffic control signal is often justified at an intersection near a ], in order to provide a preemption sequence to allow traffic queued up on the tracks an opportunity to clear the tracks before the train arrives. | * Intersection near a grade crossing. A traffic control signal is often justified at an intersection near a ], in order to provide a preemption sequence to allow traffic queued up on the tracks an opportunity to clear the tracks before the train arrives. | ||
In the US, an intersection is usually required to meet one or more of these warrants before a signal is installed. However, meeting one or more warrants does not require the installation of a traffic signal, it only suggests that they may be suitable. It could be that a ] would work better. There may be other unconsidered conditions that lead traffic engineers to conclude that a signal is undesirable. For example, it may be decided not to install a signal at an intersection if traffic stopped by it will back up and block another, more heavily trafficked intersection. Also, if a signal meets only the peak hour warrant, the advantages during that time may not outweigh the disadvantages during the rest of the day. | |||
Between 1979 and 1988, the city of ], Pennsylvania, removed 199 signals that did not meet any of the warrants. On average, the intersections had 24% fewer crashes after the unwarranted signals were removed.<ref name=CRF/> | |||
== Legal implications == | |||
] by posting the minimum fine.]] | |||
In virtually all jurisdictions{{Citation needed|date=December 2009}} in which they are used, it is an offense for motorists (and other road users) to disregard the instructions of traffic lights (or other traffic control devices). Exceptionally, it is not an offense for pedestrians to cross against a red light in the United Kingdom, where pedestrian lights officially give advice, rather than an instruction, although UK pedestrians do commit an offense if they cross a road against the signals of a police officer controlling traffic. | |||
Perhaps the most obvious common traffic-light related offense is failing to stop for a red light (in some jurisdictions, running a yellow light may also incur a penalty). Enforcement of traffic lights varies from jurisdiction to jurisdiction; some places are extremely strict, while other locales are known for traffic lights being routinely ignored by motorists, with no serious attempts by law enforcement to alter the situation. | |||
Jurisdictions differ somewhat on how to deal with "red light running" — attempts by motorists to race to an intersection while facing a yellow light, in an attempt to beat the red. In some locales, as long as the light is yellow when the motorist enters the intersection, no offense has been committed; in others, if the light turns red at any time before a motorist clears the intersection, then an offense occurs. In ] and other places, a stricter standard applies-—running a yellow light is an offense, unless the motorist is unable to stop safely. This standard has been criticized{{Citation needed|date=December 2009}} as ambiguous and difficult to enforce (red light cameras in Oregon are activated only if a motorist enters the intersection on a red). Red light cameras in ], are activated only if a motorist enters an intersection 0.3 seconds after the light has turned red.<ref>. (PDF).</ref> | |||
In some jurisdictions (such as ], Washington D.C., New York City, and the state of California),{{Citation needed|date=December 2009}} there are ordinances or by-laws against "]ing". A motorist entering an intersection (even if on a green light) but unable to proceed and who gets stranded in the intersection (when traffic ahead fails to proceed), and who remains after the light turns red (thus blocking traffic from other directions) may be cited. The definition of the intersection area is that square where the two streets overlap marked by the inner lines of each crosswalk. (Occupying the space inside the crosswalk lines is itself a traffic infraction, but different from gridlocking). This gives the meaning to the anti-gridlock slogan "don't block the box." This is sometimes used as a justification for making a turn across the opposing travel lanes on a red light at a busy intersection, by pulling partway into the intersection at a green light waiting to perform the turn, and, if oncoming traffic is not abated before the light changes to red, proceeding to turn once the light has turned red and opposing traffic has stopped. This means that at busy junctions without a protected green arrow for turning traffic, one turns after the light turns red. This maneuver is commonly referred to as "occupying the intersection" or "being legally allowed to complete one's turn". In some jurisdictions, including most American states, a vehicle already in the intersection when the light turns red legally has the right of way, and vehicles who have green must yield to the vehicle in the intersection. | |||
In ], New Brunswick, it is customary for through traffic to voluntarily yield to the first oncoming left-turning vehicle to allow it to perform a "]".{{Citation needed|date=December 2009}} This is similar to a ] performed in Melbourne, Australia, which is legal at signed intersections. | |||
] | |||
Enforcement of traffic lights is done in one of several ways: | |||
* by police officers observing traffic, and issuing citations to motorists who violate the signal | |||
* as a result of an accident investigation, if it is determined that one or more motorists ran the red light — even if the incident was not observed by a police officer | |||
* with red light cameras | |||
=== Red light cameras === | |||
{{main|Red light camera}} | |||
In some countries, ]s are used. An automated camera is connected to the triggering mechanism for the corresponding traffic light, which is targeted to photograph a vehicle and driver crossing against the light. Either the driver or the vehicle's owner (depending on local laws) are fined for the violation. In some jurisdictions, including the United States and Italy, private companies have been contracted to operate traffic-related cameras and receive a portion of the resulting revenues. In some cases red light cameras have been abused by local governments, where vehicle operators have been fined as a result of traffic systems that have been improperly modified.<ref>{{cite web |last=Peterson |first=Haley |title=Congress questions red light cameras |publisher=Washington Examiner |url=http://washingtonexaminer.com/local/congress-questions-red-light-cameras |accessdate=2010-12-14}}</ref><ref>{{cite web |url=http://www.thenewspaper.com/news/31/3128.asp |title=Italy: Prosecution Advances in Red Light Camera Fraud Scandal |date=2010-05-03 |publisher=theNewspaper.com |accessdate=2011-03-01 |quote=Mayor Adriano Alessandrini is now accused of shortening the duration of yellow lights to boost the profits of the red light camera program. The move paid off, with 2,425,801.60 euros (US $3,206,078.01) in revenue generated from motorists who did not have adequate time to stop, according to prosecution documents.}}</ref> | |||
Despite the fact that cameras can reduce the number of crashes, it has been proved that at these intersections drivers tended to react quicker to a yellow light change when stopping. <ref>{{cite web |url=http://trid.trb.org/view.aspx?id=1337520 |title=Impacts of Red Light Photo Enforcement Cameras on Clearance Lost Time at Signalized Intersections |author=Fatemeh Baratian-Ghorghi|author2= Huaguo Zhou |author3= Isaac Wasilefsky |year=2015 |work=Transportation Research Board |accessdate=17 June 2015}}</ref> The consequence of this change could be the slight decline in the intersection capacity. | |||
===Confirmation lights=== | |||
] ]] | |||
Another way police officers have begun to combat red light runners is with ''Confirmation Lights''.<ref>{{cite web|title=Traffic Signal Confirmation Light|url=http://www.cityofoviedo.net/node/1151|website=City of Oviedo, Florida|publisher=City of Oviedo, Florida|accessdate=16 January 2015}}</ref> These lights, usually blue or white, can be seen from anywhere in an intersection, making it so that officers don't have to have a line-of-sight with a red light to catch someone illegally entering an intersection. They are only on when the red light they are associated with is on. Some intersections will also have multiple confirmation lights for a single direction of travel if there are different signals for different directions. These lights are separate from the main ones, often protrude above or below the main traffic light, and are much smaller than a standard light to help avoid confusion. | |||
=== Light timing length === | |||
], Iran]] | |||
{{See also|Traffic light control and coordination}} | |||
The length of yellow lights can differ, for example in many places the length of a yellow light is usually four or five seconds, but elsewhere it may be as little as three, considerably reducing the time for reaction. It is typical for these times to vary according to the set speed limit, with longer times for higher limits. In the U.S. state of Georgia, a yellow light must be lit one second for every {{convert|10|mph}} of posted speed limit. For intersections with red light cameras, one extra second must be added.{{Citation needed|date=January 2012}} In ], yellow lights at numerous intersections have been noted with durations of approximately two seconds. In the United States, there is a recommended federal safety minimum of three seconds for yellow lights.<ref>"", '']'', 22 March 2010. Retrieved 7 November 2011.</ref> | |||
The time from when a red light is displayed and when a cross street is given a green light is usually based on the physical size of the intersection. This intervening period is called the "all-red time". A typical all-red time is two seconds to allow cars to clear the intersection. In a wider intersection, such as a four-lane road or highway intersection, the all-red time may be as much as five seconds, allowing drivers who could not or would not stop at the yellow light enough time to clear the intersection without causing a collision. However, in three locations there is no all-red time: ], B.C., ], and ], Quebec. The change is instantaneous, due to the nature of the older relay operated signals. | |||
== In other contexts == | == In other contexts == | ||
The symbolism of a traffic light (and the meanings of the three primary |
The symbolism of a traffic light (and the meanings of the three primary colours used in traffic lights) are frequently found in many other contexts. Since they are often used as single spots of colour without the context of vertical position, they are typically not comprehensible to up to one in ten males who are ].{{Citation needed|date=October 2014}} | ||
Traffic lights have also been used in pieces of artwork, particularly |
Traffic lights have also been used in computer software, such as the ] ], and in pieces of artwork, particularly '']'' in London, UK. | ||
=== Racing === | === Racing === | ||
{{see also|Racing flags}} | |||
Automobile racing circuits can also use standard traffic signals to indicate to racing car drivers the status of racing. On an oval track, four sets may be used, two facing a straight-away and two facing the middle of the 180-degree turn between straight-away. Green would indicate racing is under way, while yellow would indicate to slow or while following a pace car; red would indicate to stop, probably for emergency reasons. | |||
Automobile racing circuits can also use standard traffic signals to indicate to racing car drivers the status of racing. On an oval track, four sets may be used, two facing a straight-away and two facing the middle of the 180-degree turn between straight-away. Green would indicate racing is underway, while amber would indicate to slow or while following a pace car; red would indicate to stop, probably for emergency reasons. | |||
], a ] racing team, formerly used a traffic light system during their pit stops to signal to their drivers |
], a ] racing team, formerly used a traffic light system during their pit stops to signal to their drivers when to leave the pits.{{Citation needed|date=December 2009}} The red light was on when the tires were being changed and fuel was being added, amber was on when the tires were changed, and green was on when all work was completed. The system is (usually) completely automatic. However, the system was withdrawn after the ], due to the fact that it heavily delayed ] during the race, when he was in the lead. Usually, the system was automatic, but heavy traffic in the pit lane forced the team to operate it manually. A mechanic accidentally pressed the green light button when the fuel hose was still attached to the car, causing Massa to drive off, towing the fuel hose along. Additionally, Massa drove into the path of ], earning him a penalty. He finally stopped at the end of the pit lane, forcing Ferrari's mechanics to sprint down the whole of the pit lane to remove the hose. As a result of this, and the penalty he also incurred, Massa finished 13th. Ferrari decided to use a traditional "lollipop" for the remainder of the ] | ||
Another type of traffic light that is used in racing is the Christmas Tree, which is used in ]. The Christmas Tree has six lights: a blue staging light, three amber lights, a green light and a red light. The blue staging light is divided into two parts: Pre-stage and stage. Sometimes, there are two sets of bulbs on top of each other to represent them. Once a driver is staged at the starting line, then the starter will activate the light to commence racing, which can be done in two ways. If a Pro tree is used, then the three amber lights will flash at the same time. For the Sportsman tree, the amber light will flash from top to bottom. When the green light comes up, the race officially begins but if a driver crosses the line before that happens, then a red light will come up and that will be a foul. | Another type of traffic light that is used in racing is the Christmas Tree, which is used in ]. The Christmas Tree has six lights: a blue staging light, three amber lights, a green light, and a red light. The blue staging light is divided into two parts: Pre-stage and stage. Sometimes, there are two sets of bulbs on top of each other to represent them. Once a driver is staged at the starting line, then the starter will activate the light to commence racing, which can be done in two ways. If a Pro tree is used, then the three amber lights will flash at the same time. For the Sportsman tree, the amber light will flash from top to bottom. When the green light comes up, the race officially begins but if a driver crosses the line before that happens, then a red light will come up and that will be a foul. {{citation needed|date=March 2019}} | ||
=== As a rating mechanism === | === As a rating mechanism === | ||
{{See also|Traffic light rating system|European Union energy label}} | {{See also|Traffic light rating system|European Union energy label}} | ||
The |
The colours red, amber, and green are often used as a simple-to-understand rating system for products and processes. It may be extended by analogy to provide a greater range of intermediate colours, with red and green at the extremes.<ref>{{cite web|title=Traffic Light Song|website = ]| date=16 June 2017 |url=https://www.youtube.com/watch?v=db0HqnDU5MI |archive-url=https://ghostarchive.org/varchive/youtube/20211211/db0HqnDU5MI| archive-date=11 December 2021 |url-status=live}}{{cbignore}}</ref> | ||
== |
==In Unicode== | ||
<gallery mode="packed"> | |||
In ], the symbol for {{unichar|1F6A5|html=yes}} is HORIZONTAL TRAFFIC LIGHT and {{unichar|1F6A6|html=yes}} is VERTICAL TRAFFIC LIGHT. | |||
File:LED Traffic Light.jpg|LED traffic light (using cap visors) | |||
Portable LED traffic light.jpg|Temporary LED traffic lights with sensor in Australia | |||
Temporary traffic light.JPG|Temporary traffic light in the United Kingdom | |||
TrafficLights-HagerstownMD.jpg|Traffic light in a small intersection in ] (using tunnel visors) | |||
Cincinnati 396.JPG|Example of traffic signals mounted on gantries in downtown ], and integrated with street signage | |||
Stevens Creek Blvd traffic light.jpg|Typical example of traffic lights mounted on a wide street in California | |||
trafficsignalwide.jpg|One example of traffic lights on a suburban street in ] | |||
Led traffic lights.jpg|LED traffic lights in ], Sweden | |||
Semaforoencendido.jpg|Typical set of traffic lights in Spain | |||
SyracuseTipperaryLight.jpg | The green on top light in ], Syracuse, New York | |||
Pedestrian LED Traffic Light NYC.jpg|LED pedestrian signal in New York City | |||
Traffic light, Ashgabat.jpg|Traffic light in ] | |||
File:Reiterampel Essen.JPG|Traffic light for horse riders in ], Germany | |||
</gallery> | |||
== See also == | == See also == | ||
{{div col|colwidth=23em}} | |||
* ] | * ] | ||
* ] | |||
* ] | * ] | ||
* ] | |||
* ] | * ] | ||
* ], rail equivalent | |||
* ] for a more complete description of unusual traffic signal indications. | |||
* ] | * ] | ||
* ] | * ] | ||
* ], used in industrial process control | |||
* ] | |||
* ] | |||
* ] | * ] | ||
* ] | |||
* ] | * ] | ||
* ] | * ] | ||
* ] | |||
* ] | |||
* ] | * ] | ||
* ] | |||
* ] | |||
{{div col end}} | |||
==Notes== | ==Notes== | ||
{{ |
{{Reflist|group=note}} | ||
{{notelist|30em}} | |||
==References== | ==References== | ||
{{ |
{{Reflist|30em}} | ||
==Citations== | ==Citations== | ||
{{ |
{{Refbegin}} | ||
* City of Beacon. . Retrieved 30 |
* City of Beacon. . Retrieved 30 September 2008. | ||
* Croton-on-Hudson Historical Society. . Retrieved 30 |
* Croton-on-Hudson Historical Society. . Retrieved 30 September 2008. | ||
* Villages of Canajoharie & Palatine Bridge. . Retrieved 30 |
* Villages of Canajoharie & Palatine Bridge. . Retrieved 30 September 2008. | ||
* {{cite journal |last=Woods |first=Arthur |date=April 1916 |title=Keeping City Traffic Moving: One |
* {{cite book |last=Sessions |first=Gordon M. |date=1971 |title=Traffic devices: historical aspects thereof |location=Washington |publisher=Institute of Traffic Engineers |oclc=278619}} | ||
* {{cite journal |last=Woods |first=Arthur |date=April 1916 |title=Keeping City Traffic Moving: One of the Most Difficult of All City Problems, And The New Methods Which Have Been Devised To Solve It |journal=] |volume=XXXI |pages=621–532 |url=https://books.google.com/books?id=09_Sr9emceQC&pg=PA621 |access-date=4 August 2009 |publisher=Doubleday, Page & Company }} | |||
{{ |
{{Refend}} | ||
== External links == | == External links == | ||
{{Commons|Traffic lights}} | {{Commons and category|Traffic lights|Traffic signals}} | ||
* | * | ||
* {{Webarchive|url=https://web.archive.org/web/20130517071152/http://projects.kittelson.com/pplt/displays2.htm |date=17 May 2013 }} | |||
* by ], ]: demonstrates that there are "seven distinct light cycles that will prevent collisions." | |||
* | |||
* | |||
* ] | |||
* | |||
* ] | |||
* | |||
* | |||
* ] | |||
* ] | |||
* , digitized ] photograph from the ] Digital Collections | * , digitized ] photograph from the ] Digital Collections | ||
* | |||
{{Traffic signs}} | {{Traffic signs}} | ||
{{Artificial light sources}} | {{Artificial light sources}} | ||
{{Authority control}} | |||
] | |||
] | ] | ||
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Latest revision as of 02:31, 16 December 2024
Signaling device to control competing flows of traffic This article is about lights used for signalling. For other uses, see Traffic light (disambiguation). "Stoplight" redirects here. For other uses, see Stoplight (disambiguation).
Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic.
Traffic lights normally consist of three signals, transmitting meaningful information to road users through colours and symbols, including arrows and bicycles. The regular traffic light colours are red to stop traffic, amber for traffic change, and green for allowing the traffic, arranged vertically or horizontally in that order. Although this is internationally standardised, variations in traffic light sequences and laws exist on national and local scales.
Traffic lights were first introduced in December 1868 on Parliament Square in London to reduce the need for police officers to control traffic. Since then, electricity and computerised control have advanced traffic light technology and increased intersection capacity. The system is also used for other purposes, including the control of pedestrian movements, variable lane control (such as tidal flow systems or smart motorways), and railway level crossings.
History
Main article: History of traffic lightsThe first system of traffic signals, which was a semaphore traffic signal, was installed as a way to replace police officer control of vehicular traffic outside the Houses of Parliament in London on 9 December 1868. This system exploded on 2 January 1869 and was thus taken down. But this early traffic signal led to other parts of the world implementing similar traffic signal systems. In the first two decades of the 20th century, semaphore traffic signals like the one in London were in use all over the United States. These traffic signals were controlled by a traffic officer who would change the commands on the signal to direct traffic.
In 1912, the first electric traffic light was developed by Lester Wire, a policeman in Salt Lake City, Utah. It was installed by the American Traffic Signal Company on the corner of East 105th Street and Euclid Avenue in Cleveland, Ohio, on August 5, 1914. The first four-way, three-colour traffic light was created by William Potts in Detroit, Michigan in 1920. His design was the first to include an amber 'caution' light along with red and green lights. Potts was Superintendent of Signals for the Police Department of Detroit. He installed automatic four-way, three-colour traffic lights in 15 towers across Detroit in 1921. By 1922, traffic towers were beginning to be controlled by automatic timers more widely. The main advantage of the use of the timer was that it saved cities money by replacing traffic officers. The city of New York was able to reassign all but 500 of its 6,000 officers working on the traffic squad, saving the city $12,500,000.
In 1923, Garrett Morgan patented a design of a manually operated three-way traffic light with moving arms.
The control of traffic lights made a big turn with the rise of computers in America in the 1950s. One of the best historical examples of computerized control of lights was in Denver in 1952. In 1967, the city of Toronto was the first to use more advanced computers that were better at vehicle detection. The computers maintained control over 159 signals in the cities through telephone lines.
Vehicular signals
A set of lights, known as a signal head, may have one, two, three, or more aspects. The most common signal type has three aspects facing the oncoming traffic: red on top, amber (yellow) below, and green below that. Additional aspects may be fitted to the signal, usually to indicate specific restrictions or filter movements.
Meanings of signals
The 1968 Vienna Convention on Road Signs and Signals Chapter III provides international standards for the setup of traffic signal operations. Not all states have ratified the convention. A three-colour signal head should have three non-flashing lights which are red, amber, and green, either arranged horizontally (on the side opposite to the direction of traffic) or vertically (with red on top). A two-colour signal head may be used in temporary operation and consists of red and green non-flashing lights. In both cases, all lights should be circular or arrow-shaped. Permissible signals for regulating vehicle traffic (other than public transport vehicles) are outlined in Article 23:
Light type | Meaning | |
---|---|---|
Non-flashing | Red | Traffic may not proceed beyond the stop line, or otherwise enter the intersection |
Red/Amber | The signal is about to change, but the red light rules do apply | |
Amber | Traffic may not pass the stop line or enter the intersection, unless it cannot safely stop when the light shows | |
Green | Traffic may proceed, unless it would not clear the intersection before the next change of phase | |
Flashing | Red | Traffic must not pass the stop line at a level crossing, approach to swing bridge or ferry landing stages, emergency vehicles entering the road, or on the approach to low-flying aircraft. In addition, to attract attention in these locations, it is also equipped with additional alarms and voice prompts |
Amber | Traffic may proceed with caution |
Green arrows are added to signals to indicate that drivers can travel in a particular direction, while the main lights for that approach are red, or that drivers can only travel in one particular direction. Alternatively, when combined with another green signal, they may indicate that turning traffic has priority over oncoming traffic (known as a "filter arrow"). Flashing amber arrows typically indicate that road users must give way (to other drivers and pedestrians) before making a movement in the direction of the arrow. These are used because they are safer, cause less delay, and are more flexible. Flashing amber arrows will normally be located below the solid amber.
Green arrows
Arrow aspects may be used to permit certain movements or convey other messages to road users. A green arrow may display to require drivers to turn in a particular direction only or to allow drivers to continue in a particular direction when the signal is red. Generally, a green phase is illuminated at the beginning of the green phase (a "leading turn") or at the end of the green phase (a "lagging turn"). An 'indicative arrow' may be displayed alongside a green light. This indicates to drivers that oncoming traffic is stopped, such that they do not need to give way to that traffic when turning across it. As right-turning traffic (left-side drive) or left-turning traffic (right-side drive) does not normally have priority, this arrow is used to allow turning traffic to clear before the next phase begins.
Some variations exist on this set up. One version is a horizontal bar with five lights – the green and amber arrows are located between the standard green and amber lights. A vertical five-light bar holds the arrows underneath the standard green light (in this arrangement, the amber arrow is sometimes omitted, leaving only the green arrow below the steady green light, or possibly an LED-based device capable of showing both green and amber arrows within a single lamp housing).
A third type is known as a "doghouse" or "cluster head" – a vertical column with the two normal lights is on the right side of the signal, a vertical column with the two arrows is located on the left, and the normal red signal is in the middle above the two columns. Cluster signals in Australia and New Zealand use six signals, the sixth being a red arrow that can operate separately from the standard red light. In a fourth type, sometimes seen at intersections in Ontario and Quebec, Canada, there is no dedicated left-turn lamp per se. Instead, the normal green lamp flashes rapidly, indicating permission to go straight as well as make a left turn in front of opposing traffic, which is being held by a steady red lamp. (This "advance green", or flashing green can be somewhat startling and confusing to drivers not familiar with this system. This also can cause confusion amongst visitors to British Columbia, where a flashing green signal denotes a pedestrian-controlled crosswalk. For this reason, Ontario is phasing out the use of flashing green signals and instead replacing them with arrows.)
Countdown lights
Popular in Vietnam and China, countdown lights are additional lights installed next to (or above or below) the main signal lights. The countdown light is displayed by a countdown number with different colors (usually red, yellow, green), matching the color of the light on. When the light counts to "0" (or 1), the main light color immediately changes. Countdown lights may have zeros in the tens or none, some countdown lights may flash when getting ready to zero. Yellow lights can also have countdown lights, but most lights do not. Usually the countdown light has 2 digits, in case the time of the main light (usually the red light, rarely the green light) is longer than 100 seconds, depending on the type of light, the following possibilities may occur:
- Lights have not counted down, when 99 seconds are left, start counting. During the standby time, the light may be displayed as "99", "00", "--" or not displayed.
- Last 2 digits count light of the timeout (the counter light is 15 while the time is 115 seconds, there are some types of lights that count as "-9" or "9-" when the time is 109 seconds)
- Tens digit on the displayer becomes a letter. Displaying A0 for 100 seconds, B0 for 110 seconds, so forth.
- Displaying only last 2 digits but with flashing to indicate it's more than 100.
Issue about yellow light dilemma zone in South Korea
In South Korea, the yellow light dilemma zone is not legally recognized. In other words, when the yellow light is on, traffic may not pass the stop line or enter the intersection even if cannot safely stop when the light shows.
This has been reaffirmed by the ruling of the Supreme Court of Korea in May 2024, for a case where the driver was speeding at 62 km/h in a street limited up to 40 km/h (55 % upper than the allowed speed).
Criticism in South Korea says that this is unrealistic and unreasonable. In addition, this can cause multiple collisions due to sudden braking.
In 2016 when speed limit was up to 60 km/h, proposed alternatives to this kind of collision were only roundabouts, speed compliance increase and speed practice reduction or elderly zones are also proposed solutions.
Yellow trap
Without an all-red phase, cross-turning traffic may be caught in a yellow trap. When the signal turns yellow, a turning driver may assume oncoming traffic will stop and a crash may result. For this reason, the US bans sequences that may cause a yellow trap. This can also happen when emergency vehicles or railroads preempt normal signal operation. In the United States, signs reading "Oncoming traffic has extended green" or "Oncoming traffic may have extended green" must be posted at intersections where the "yellow trap" condition exists.
Variations
Main article: Variations in traffic light operationThe United States is not party to the Vienna Convention; rather, the Manual on Uniform Traffic Control Devices (MUTCD) outlines correct operation in that country. In the US, a single signal head may have three, four, or five aspects (though a single aspect green arrow may be displayed to indicate a continuous movement). The signals must be arranged red, amber, and green vertically (top to bottom) or horizontally (left to right). In the US, a single-aspect flashing amber signal can be used to raise attention to a warning sign and a single-aspect flashing red signal can be used to raise attention to a "stop", "do not enter", or "wrong way" sign. Flashing red or amber lights, known as intersection control beacons, are used to reinforce stop signs at intersections. The MUTCD specifies the following vehicular signals:
Signal | Meaning (steady) | Meaning (flashing) |
---|---|---|
Circular green |
Traffic can proceed in any permitted direction, yielding to pedestrians in a crosswalk or other vehicles when turning | Not to be used |
Green arrow |
Traffic can proceed in the direction shown by the arrow, yielding to any pedestrians in a crosswalk or other vehicles in the intersection | |
Circular yellow |
The green movement is being terminated and a red signal will soon be displayed | Traffic can cautiously enter the intersection, yielding to pedestrians and other vehicles |
Yellow arrow |
The green or flashing arrow movement is being terminated | Traffic can cautiously enter the intersection to make the movement displayed by the arrow, yielding to pedestrians and other vehicles |
Circular red |
Unless another signal permits, traffic shall not enter the intersection except to lawfully turn on red | Traffic must stop before entering the intersection, but may then treat the signal by the same rules as a STOP sign. |
Red arrow |
Traffic shall not make the movement displayed by the arrow | Traffic must stop before entering the intersection, but may then treat the signal by the same rules as a stop sign to make the movement displayed by the arrow. |
In the Canadian province of Quebec and the Maritime provinces, lights are often arranged horizontally, but each aspect is a different shape: red is a square (larger than the normal circle) and usually in pairs at either end of the fixture, amber is a diamond, and green is a circle. In many southern and southwestern U.S. states, most traffic signals are similarly horizontal in order to ease wind resistance during storms and hurricanes. Japanese traffic signals mostly follow the same rule except that the green "go" signals are referred to as 青 (ao), typically translated as "blue", reflecting a historical change in the Japanese language. As a result, Japanese officials decreed in 1973 that the "go" light should be changed to the bluest possible shade of green, bringing the name more in line with the color without violating the international "green means go" rule.
In the UK, normal traffic lights follow this sequence:
- Red – Stop, do not proceed
- Red and Amber – Get ready to proceed, but do not proceed yet
- Green – Proceed if the intersection or crossing is clear; vehicles are not allowed to block the intersection or crossing
- Amber – Stop, unless it is unsafe to do so
A speed sign is a special traffic light, variable traffic sign, or variable-message sign giving drivers a recommended speed to approach the next traffic light in its green phase and avoid a stop due to reaching the intersection when lights are red.
Pedestrian signals
Further information: Pedestrian crossingPedestrian signals are used to inform pedestrians when to cross a road. Most pedestrian signal heads will have two lights: a 'walk' light (normally a walking human figure, typically coloured green or white) and a 'don't walk' light (normally either a red or orange man figure or a hand), though other variations exist.
Country/ies | Sequence | Notes |
---|---|---|
Australia, New Zealand, Philippines | Green man: safe to cross
Flashing red man: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely Red man: do not cross |
Several intersections in Wellington, New Zealand, have alternative green man figures. Eight intersections near Parliament Buildings have silhouettes of suffragette Kate Sheppard, while four intersections along Cuba Street have silhouettes of drag performer and LGBT rights activist Carmen Rupe. |
China | Green: safe to cross
Red: do not cross Amber (steady, after green, before red): continue to cross only if unable to stop safely Flashing amber: cross with caution (often used in low-traffic crossing or after midnight) |
|
Japan | Blue or green man: safe to cross (cyclists may cross or turn left)
Flashing blue or green man: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely Red standing man: do not cross |
|
Germany, Czechia, Central Europe | Green: safe to cross
Amber: continue to cross only if unable to stop safely Flashing amber: cross with caution, obey signage (used when lights are out of order or shut down) Red: do not cross Red and amber: do not cross, prepare for green |
In Germany, Ampelmännchen pedestrian traffic signals have come to be seen as a nostalgic sign for the former German Democratic Republic.
In Germany, the fine for crossing a red light if caught is as of 2019 between €5 and €10. |
United Kingdom, Ireland, Hong Kong, Switzerland, Macao | Green walking man: safe to cross
Flashing green man or no man: do not start to cross (only at mid-block crossings); if it appears during crossing, then continue to cross if unable to stop safely Red standing man: do not cross |
In the United Kingdom, there is no direct offence committed if a pedestrian fails to obey crossing signals and many lights commonly only use two still images – a green walking person and a red standing man, this being the general case where the crossing is at a road junction and the pedestrian signals are in combination with those controlling vehicular traffic. |
United States, Canada, Mexico (Tijuana), Philippines (Makati, Davao) | Formerly signals used the text:
WALK DONT WALK Modern version: White walking man: cross with caution Flashing orange stophand: do not start to cross; if it appears during crossing, then continue to cross if unable to stop safely Orange stophand: do not enter the intersection |
The U.S. state of Massachusetts allows an unusual indication variation for pedestrian movement. At signalized intersections without separate pedestrian signal heads, the traffic signals may be programmed to turn red in all directions, followed by a steady display of amber lights simultaneously with the red indications. During this red-plus-amber indication, the intersection is closed to vehicular traffic and pedestrians may cross, usually in whatever direction they choose. |
Israel | Red standing man: do not cross; if it appears during crossing, then continue to cross if unable to stop safely
Green walking man: safe to cross |
|
France | green and light, traditionally and in compliance with the international conventions.
Red Man: Do Not Cross. If it appears during crossing, then continue to cross if unable to stop safely. Green Man: Safe to Cross. |
In 2023, a two year experiment was allowed to start on 8 intersections experimenting blinking yellow light and 7 other one frozen yellow light. |
Where pedestrians need to cross the road between junctions, a signal-controlled crossing may be provided as an alternative to a zebra crossing or uncontrolled crossing. Traffic lights are normally used at crossings where vehicle speeds are high, where either vehicle or pedestrian flows are high or near signalised junctions. In the UK, this type of crossing is called a pelican crossing, though more modern iterations are puffin and pedex crossings. In the UK, these crossings normally need at least four traffic signals, which are of a regular type (red, amber, and green), two facing in each direction. Furthermore, pedestrians will be provided with push buttons and pedestrian signals, consisting of a red and green man. Farside signals are located across the crossing, while nearside signals are located below the traffic lights, facing in the direction of oncoming traffic. A HAWK beacon is a special type of traffic used in the US at mid-block crossings. These consist of two red signals above a single amber signal. The beacon is unlit until a pedestrian pushes the cross button. Then an amber light will show, followed by both red lights, at which point the 'Walk' symbol will illuminate for pedestrians. At the end of the crossing phase, the 'Don't Walk' symbol will flash, as will the amber traffic light.
Pedestrians are usually incorporated into urban signalised junctions in one of four ways: no facilities, parallel walk, walk with traffic, or all-red stages. No facilities may be provided if pedestrian demand is low, in areas where pedestrians are not permitted, or if there is a subway or overpass. No provision of formal facilities means pedestrians will have to self-evaluate when it is safe to cross, which can be intimidating for pedestrians. With a "parallel walk" design, pedestrians walk alongside the traffic flow. A leading pedestrian interval may be provided, whereby pedestrians get a "walk" signal before the traffic gets a green light, allowing pedestrians to establish themselves on the crossing before vehicles begin to turn, to encourage drivers to give way. A 'walk with traffic' facility allows pedestrians to go at the same time as other traffic movements with no conflict between movements. This can work well on one-way roads, where turning movements are banned or where the straight-ahead movement runs in a different stage from the turning movement. A splitter island could also be provided. Traffic will pass on either side of the island and pedestrians can cross the road safely between the other flows.
An all-red stage, also known as a full pedestrian stage, a pedestrian scramble or a Barnes Dance, holds all vehicular traffic at the junction to allow pedestrians time to safely cross without conflict from vehicles. It allows allows the use of diagonal crossings. This may require a longer cycle time and increase pedestrian wait periods, though the latter can be eased by providing two pedestrian stages.
Pedestrian countdown timers are becoming common at urban signal-controlled crossings. Where a pedestrian countdown is shown, it is normally used in conjunction with the flashing hand signal (in the US and Canada) or blackout period (UK), showing the amount of time remaining in seconds until the end of the flashing hand or blackout. Pedestrian countdown timers do not significantly increase or reduce the number of red- and amber-light running drivers. Studies have found that pedestrian countdown timers do significantly improve pedestrian compliance over traditional pedestrian signals; however, results are mixed.
Smartphone Zombie ribbon
As the 12 to 45% of pedestrian deaths caused by 'pedestrian distraction' has been linked to cell phone usage, some cities (including Sydney, Seoul, Augsburg, Bodegraven, Tel Aviv, and Singapore) have installed LED strips embedded in the sidewalk before crosswalks to warn distracted pedestrians of immanent pedestrian crossings. This additional signal, which is synchronized with conventional signals, aims to decrease injury rates by telling distracted pedestrians when it is safe to cross the road without them having to lift their head.
- Smartphone zombie light in green
- Smartphone zombie light in green, close up
- Smartphone zombie light in red
- Smartphone zombie light in red, close up
Auditory and tactile signals
In some jurisdictions such as Australia, pedestrian lights are associated with a sound device, for the benefit of blind and visually impaired pedestrians. These make a slow beeping sound when the pedestrian lights are red and a continuous buzzing or fast beeping sound when the lights are green. In the Australian States of Queensland, New South Wales, Victoria, and Western Australia, the sound is produced in the same unit as the push buttons. In a circle above the button, the sound is produced and can be felt along with a raised arrow that points in the direction to walk. This system of assistive technology is also widely used at busy intersections in Canadian cities. In the United Kingdom, the Puffin crossings and their predecessor, the Pelican crossing, will make a fast beeping sound to indicate that it is safe to cross the road. The beeping sound is disabled during the nighttime so as not to disturb any nearby residents.
In some states in the United States, at some busy intersections, buttons will make a beeping sound for blind people. When the light changes, a speaker built into the button will play a recording to notify blind people that it is safe to cross. When the signal flashes red, the recording will start to count down with the countdown timer. In several countries such as New Zealand, technology also allows deaf and blind people to feel when lights have changed to allow safe crossing. A small pad, housed within an indentation in the base of the box housing the button mechanism, moves downwards when the lights change to allow crossing. This is designed to be felt by anyone waiting to cross who has limited ability to detect sight or sound. In Japan, a traffic light emits an electronic sound that mimics the sound of birdsong to help the visually impaired. Some traffic lights fix the order and type of sound so that they can tell which direction is a green light. In general, "Piyo" (peep) and "Piyo-piyo", which is a small bird call, and "Kakkō" and "Ka-kakkō", which is a cuckoo call, are associated with this system. Some pedestrian crossings in Lithuania make a slow beeping sound indicating that the traffic light is about to turn off.
Cycle signals
Further information: Protected intersectionWhere cycle lanes or cycle tracks exist on the approach to a signal-controlled junction, it must be considered how to incorporate cyclists safely into the junction to reduce conflict between motor vehicles and cyclists.
An advanced stop line can be placed after the stop line at traffic lights. This allows cyclists to position themselves in front of traffic at a red light and get a headstart.
In the US, design advice typically advises that the cycle lane should continue through the junction to the left of the right-turn lane; however, this creates conflict where motor vehicles wish to enter the right lane, as they must cross the cycle lane at a bad angle.
Under Dutch engineering principles, cyclists are instead kept to the right of the junction, with protected kerbs. This improves safety by putting cyclists into the eyeline of motor vehicles at the stop line, allowing cyclists a headstart over turning traffic. This design also allows cyclists to complete far-side turns without having to wait in the centre of the junction. UK engineers have innovated on this design through the Cycle Optimised Protected Signals (CYCLOPS) junction, e.g. in Manchester. This places the cycle track around the edge of the signal junction and gives cyclists and pedestrians a single all-red phase, entirely separate from motor traffic and shortens pedestrian crossing times.
Alternatively, cyclists can be considered pedestrians on approach to a junction, or where a cycle track crosses a road and combined pedestrian-cyclist traffic lights (known as Toucan crossings in the UK) can be provided.
Public transport signals
Traffic lights for public transport often use signals that are distinct from those for private traffic. They can be letters, arrows or bars of white or (an LED 100-watt typical) coloured light.
Transit signals in North America
MUTCD specifies a standard vertically oriented signal with either two or three lenses, displaying white lines on a black background.
Some systems use the letter B for buses and T for trams. The METRO light rail system in Minneapolis, Minnesota, the Valley Metro Rail in Phoenix, Arizona, and the RTA Streetcar System in New Orleans use a simplified variant of the Belgian/French system in the respective city's central business district where only the "go" and "stop" configurations are used. A third signal equal to amber is accomplished by flashing the "go" signal.
Public transport signals in Europe
In some European countries and Russia, dedicated traffic signals for public transport (tram, as well any that is using a dedicated lane) have four white lights that form the letter T. If the three top lamps are lit, this means "stop". If the bottom lamp and some lamps on the top row are lit, this means permission to go in a direction shown. In the case of a tram signal, if there are no tram junctions or turns at an intersection, a simpler system of one amber signal in the form of the letter T is used instead; the tram must proceed only when the signal is lit.
In North European countries, the tram signals feature white lights of different forms: "S" for "stop", "—" for "caution" and arrows to permit passage in a given direction. In Sweden, All signals use white lighting and special symbols ("S", "–" and an arrow) to distinguish them from regular signals.
The Netherlands uses a distinctive "negenoog" (nine-eyed) design shown on the top row of the diagram; bottom row signals are used in Belgium, Luxembourg, France, and Germany. The signals mean (from left to right): "go straight ahead", "go left", "go right", "go in any direction" (like the "green" of a normal traffic light), "stop, unless the emergency brake is needed" (equal to "amber"), and "stop" (equal to "red").
Public transport signals in the Asia-Pacific region
In Japan, tram signals are under the regular vehicle signal; however, the colour of the signal intended for trams is orange. The small light at the top tells the driver when the vehicle's transponder signal is received by the traffic light. In Hong Kong, an amber T-signal is used for trams, in place of the green signal. In addition, at any tramway junction, another set of signals is available to indicate the direction of the tracks. In Australia and New Zealand, a white "B" or "T" sometimes replaces the green light indicating that buses or trams (respectively) have right of way.
Preemption and priority
Main articles: Traffic signal preemption and Bus prioritySome regions have signals that are interruptible, giving priority to special traffic, usually emergency vehicles such as firefighting apparatus, ambulances, and police cars. Most of the systems operate with small transmitters that send radio waves, infrared signals, or strobe light signals that are received by a sensor on or near the traffic lights. Some systems use audio detection, where a certain type of siren must be used and detected by a receiver on the traffic light structure.
Upon activation, the normal traffic light cycle is suspended and replaced by the "preemption sequence": the traffic lights to all approaches to the intersection are switched to "red" with the exception of the light for the vehicle that has triggered the preemption sequence. Sometimes, an additional signal light is placed nearby to indicate to the preempting vehicle that the preempting sequence has been activated and to warn other motorists of the approach of an emergency vehicle. The normal traffic light cycle resumes after the sensor has been passed by the vehicle that triggered the preemption.
In lieu of preemptive mechanisms, in most jurisdictions, emergency vehicles are not required to respect traffic lights. However, emergency vehicles must slow down, proceed cautiously and activate their emergency lights to alert oncoming drivers to the preemption when crossing an intersection against the light.
Unlike preemption, which immediately interrupts a signal's normal operation to serve the preempting vehicle and is usually reserved for emergency use, "priority" is a set of strategies intended to reduce delay for specific vehicles, especially mass transit vehicles such as buses. A variety of strategies exist to give priority to transit but they all generally work by detecting approaching transit vehicles and making small adjustments to the signal timing. These adjustments are designed to either decrease the likelihood that the transit vehicle will arrive during a red interval or decrease the length of the red interval for those vehicles that are stopped. Priority does not guarantee that transit vehicles always get a green light the instant they arrive as preemption does.
Operation
Main article: Traffic light control and coordinationA variety of different control systems are used to operate signal cycles smoothly, ranging from simple clockwork mechanisms to sophisticated computerised control systems. Computerised systems are normally actuated, i.e. controlled by loop detectors or other sensors on junction approaches. Area-wide coordination can allow green wave systems to be set up for vehicles or cycle tracks. Smart traffic light systems combine traditional actuation, a wider array of sensors and artificial intellegence to further improve performance of signal systems. A traffic signal junction or crossing is typically controlled by a controller mounted inside a cabinet nearby.
"Phases" (or "signal groups" in Australia and New Zealand) are indications show simultaneously, e.g. multiple green lights which control the same traffic approach. A "movement" is any path through the junction which vehicles or pedestrians are permitted to take, which is "conflicting" if these paths cross one another. A stage (or "phase" in ANZ) is a group of non-conflicting phases which move at the same time. The stages are collectively known as a "cycle". The time between two conflicting green phases is called an "intergreen period", which is set at an appropriate length for the junction to safely clear, especially for turning traffic which may be waiting in the centre of the junction. This often results in an all red stage, when all approaches are shown a red light and no vehicle can proceed. This all red is sometimes extended to allow a pedestrian scramble, where pedestrians can cross the empty junction in any direction all at once. Some signals have no "all red" phase: the light turns green for cross traffic the instant the other light turns red.
Many traffic light installations are fitted with vehicle actuation, i.e. detection, to improve the flexibility of traffic systems to respond to varying traffic flows. Detectors come in the form of digital sensors fitted to the signal heads or induction loops within the road surface. Induction loops are beneficial due to their smaller chance of breakdown, but their simplicity can limit their ability to handle some situations, particularly involving lighter vehicles such as motorcycles or pedal cycles. This situation most often occurs at times of day when other traffic is sparse as well as when the small vehicle is coming from a direction that does not have a high volume of traffic.
Timing
Main article: Signal timingThe timing of the intergreen is usually based on the size of the intersection, which can range from two to five seconds. Modelling programs include the ability to calculate intergreen times automatically. Intergreen periods are determined by calculating the path distance for every conflict point in the junction, which is the distance travelled to the conflict point by the movement losing right of way minus the distance travelled to the same conflict point by the movement gaining right of way using the possible conflict points (including with pedestrians) and calculating both the time it would take the last vehicle to clear the furthest collision point and the first vehicle from the next stage to arrive at the conflict point. At actuated junctions, integreens can be varied to account for traffic conditions.
Engineers also need to set the amber timings (and red-amber, where appropriate), which is normally standardised by a traffic authority. For example, in the UK, the amber time is fixed nationally at three seconds and the red-amber time at two seconds, which results in a minimum intergreen time of five seconds (plus any all-red time). The US also uses a minimum of three seconds, but local traffic authorities can make timings longer, especially on wider, suburban roads. This variation has resulted in controversy when municipalities with shorter amber times use red light cameras. Where pedestrian signals are used, the timing of the "inivitation to cross" – the period where a steady walk signal shows – and clearance periods – time when the walk signal flashes or no signal is shown – need to be calculated. This is normally set against a design speed, e.g. 1.2 m/s (3.9 ft/s). Similarly, these can be made extendable using sensors, allowing slower-moving pedestrians more time to cross the street.
Design guidance
National or sub-national highway authorities often issue guidance documents on the specification of traffic signals and design of signalised intersections according to national or local regulations. For example, in the United States the Federal Highway Administration issues the Manual on Uniform Traffic Control Devices and the Signalized Intersections Information Guide, which is a synthesis of best practices and treatments to help practitioners make informed decisions.
Variable lane control
Main article: Lane control lightsVariable lane control is a form of intelligent transportation systems which involve the use of lane-use control signals, typically on a gantry above a carriageway. These lights are used in tidal flow systems to allow or forbid traffic to use one or more of the available lanes by the use of green lights or arrows (to permit) or by red lights or crosses (to prohibit). Variable lane control may be in use at toll plazas to indicate open or closed booths; during heavy traffic to facilitate merging traffic from a slip road.
In the US, most notably the Southeastern, there often is a "continuous-flow" lane. This lane is protected by a single, constant-green arrow pointing down at the lane(s) permitting the continuous flow of traffic, without regard to the condition of signals for other lanes or cross streets. Continuous lanes are restricted in that vehicles turning from a side street may not cross over the double white line to enter the continuous lane, and no lane changes are permitted to the continuous lane from an adjacent lane or from the continuous lane to an adjacent lane until the double white line has been passed. Some continuous lanes are protected by a raised curb located between the continuous lane and a normal traffic lane, with white and/or amber reflective paint or tape, prohibiting turning or adjacent traffic from entering the lane.
Continuous-flow traffic lanes are found only at "T" intersections where there is no side street or driveway entrance on the right side of the main thoroughfare; additionally, no pedestrians are permitted to cross the main thoroughfare at intersections with a continuous-flow lane, although crossing at the side street may be permitted. Intersections with continuous-flow lanes will be posted with a white regulatory sign approximately 500 ft (150 m) before the intersection with the phrase, "right lane continuous traffic," or other, similar, wording. If the arrow is extinguished for any reason, whether by malfunction or design, traffic through the continuous lane will revert to the normal traffic pattern for adjacent lanes, except that turning or moving into or out of the restricted lane is still prohibited.
Waterways and railways
The three-aspect standard is also used at locks on the Upper Mississippi River. Red means that another vessel is passing through. Amber means that the lock chamber is being emptied or filled to match the level of the approaching vessel. After the gate opens, green means that the vessel may enter.
Railroad signals, for stopping trains in their own right of way, generally use the opposite positioning of the colours; that is, for signals above the driver's eyeline, green on top and red below is the standard placement of the signal colours on railroad tracks. There are three reasons for this variation: there is no risk that railway signals will be masked by a tall vehicle between the driver and the signal; train speeds in fog are much higher than for road vehicles, so it is important that the most restrictive signal is closest to the driver's eyeline; and with railway signals often in exposed rural locations, there is a risk of any signal other than the bottom one being masked by snow building up on the hood of the signal below.
Rules
Main article: Rules for traffic lightsTraffic lights control flows of traffic using social norms and legal rules. In most jurisdictions, it is against the law to disobey traffic signals and the police, or devices such as red light cameras, can issue fines or other penalties – and in some cases prosecute – drivers who break those laws. US-based studies have found that the majority of drivers think that it is dangerous to run a red light at speed and the most common reason for red light running include inattentive driving, following an oversized vehicle or during inclement weather.
The rules governing traffic light junctions for vehicles differ by jurisdiction. For example, it is common in North America that drivers can turn kerb-to-kerb (i.e. turning right at most junctions), even when a red light shows. On the other hand, this turn on red rule is uncommon in Europe, unless an arrow signal or traffic sign specifically permits it.
Design
Bulbs
Conventional traffic signal lighting, still common in some areas, uses a standard light bulb. The light then bounces off a mirrored glass or polished aluminium reflector bowl, and out through a polycarbonate plastic or glass signal lens. In some signals, these lenses were cut to include a specific refracting pattern. Traditionally, incandescent and halogen bulbs were used. Because of the low efficiency of light output and a single point of failure (filament burnout), some traffic authorities are choosing to retrofit traffic signals with LED arrays that consume less power, have increased light output, and last significantly longer. Moreover, in the event of an individual LED failure, the aspect will still operate albeit with a reduced light output. The light pattern of an LED array can be comparable to the pattern of an incandescent or halogen bulb fitted with a prismatic lens.
The low energy consumption of LED lights can pose a driving risk in some areas during winter. Unlike incandescent and halogen bulbs, which generally get hot enough to melt away any snow that may settle on individual lights, LED displays – using only a fraction of the energy – remain too cool for this to happen. As a response to the safety concerns, a heating element on the lens was developed.
Programmable visibility signals
Traffic signals installed in Shelton, Washington, seen off-axis from the intended viewing area (top) and from the signal's intended viewing area (bottom).From off-axis, these signals appear to be "off" or invisible to adjacent lanes of traffic during the daytime. Only a faint glow can be seen when viewed at night.Signals such as the 3M High Visibility Signal utilize light-diffusing optics and a Fresnel lens to create the signal indication. The light from a 150 W PAR46 sealed-beam lamp in these "programmable visibility" signals passes through a set of two glass lenses at the back of the signal. The first lens, a frosted glass diffusing lens, diffuses the light into a uniform ball of light around five inches in diameter. The light then passes through a nearly identical lens known as an optical limiter (3M's definition of the lens itself), also known as a "programming lens", also five inches in diameter.
Using a special aluminium foil-based adhesive tape, these signals are "masked" or programmed by the programming lens so that only certain lanes of traffic will view the indication. At the front of these programmable visibility signals is a 12" Fresnel lens, each lens tinted to meet United States Institute of Transportation Engineers (ITE) chromaticity and luminance standards. The Fresnel lens collimates the light output created by the lamp and creates a uniform display of light for the lane in which it is intended.
In addition to being positioned and mounted for desired visibility for their respective traffic, some traffic lights are also aimed, louvered, or shaded to minimize misinterpretation from other lanes. For example, a Fresnel lens on an adjacent through-lane signal may be aimed to prevent left-turning traffic from anticipating its own green arrow. Intelight Inc. manufactures a programmable traffic signal that uses a software-controlled LED array and electronics to steer the light beam toward the desired approach. The signal is programmed unlike the 3M and McCain models. It requires a connection to a laptop or smartphone with the manufacturer's software installed. Connections can be made directly with a direct-serial interface kit, or wirelessly with a radio kit over WIFI to the signal. In addition to aiming, Fresnel lenses, and louvers, visors and back panels are also useful in areas where sunlight would diminish the contrast and visibility of a signal face. Typical applications for these signals were skewed intersections, specific multi-lane control, left-turn pocket signals, or other areas where complex traffic situations existed.
Size
In the United States, traffic lights are currently designed with lights approximately 12 inches (300 mm) in diameter. Previously the standard had been 8 inches (200 mm); however, those are slowly being phased out in favour of the larger and more visible 12 inch lights. Variations used have also included a hybrid design, which had one or more 12 inch lights along with one or more lights of 8 inches (200 mm) on the same light.
In the United Kingdom, 12-inch lights were implemented only with Mellor Design Signal heads designed by David Mellor. These were designed for symbolic optics to compensate for the light loss caused by the symbol. However, following a study sponsored by the UK Highways Agency and completed by Aston University, Birmingham, UK, an enhanced optical design was introduced in the mid-1990s. Criticism of sunlight washout (cannot see the illuminated signal due to sunlight falling on it), and sun-phantom (signal appearing to be illuminated even when not due to sunlight reflecting from the parabolic mirror at low sun angles), led to the design of a signal that used lenslets to focus light from a traditional incandescent bulb through apertures in a matt black front mask. This cured both problems in an easily manufactured solution. This design proved successful and was taken into production by a number of traffic signal manufacturers through the engineering designs of Dr. Mark Aston, working firstly at the SIRA Ltd in Kent, and latterly as an independent optical designer.
The manufacturers took a licence for the generic design from the Highways Agency, with Dr. Aston engineering a unique solution for each manufacturer. Producing both bulb and LED versions of the signal aspects, these signals are still the most common type of traffic light on UK roads. With the invention of anti-phantom, highly visible Aston lenses, lights of 8 inches (200 mm) could be designed to give the same output as plain lenses, so a larger surface area was unnecessary. Consequently, lights of 12 inches (300 mm) are no longer approved for use in the UK and all lights installed on new installations have to be 200 mm (8 in) in accordance with TSRGD (Traffic Signs Regulations and General Directions). Exemptions are made for temporary or replacement signals.
Mounting and placement
- Part time pole/pedestal-mounted traffic lights in Canberra, Australia
- Mast-arm traffic lights in Ekiti State, Nigeria
- Horizontal traffic lights mounted on a footbridge in Taipei, Taiwan
- A dummy light in Canajoharie, New York. It was removed in 2021.
The MUTCD identifies five types of traffic light mounts. On pedestals, signal heads are mounted on a single pole (this is the normal installation method for the UK). On mast arms, signal heads are mounted on a rigid arm over the road protuding from the pole. On strained poles, signals are suspended over a roadway on a wire, attached to poles at opposite kerbs. This is the most common installation method in the United States. Unipoles are similar to strain poles, but a single structure over the road, rather than two poles linked with wire. Finally, signals can be attached to existing structures such as an overpass. Dummy lights are traffic signs located in the centre of a junction, which operate on a fixed cycle. These have generally been decommissioned due to safety concerns; however, a number remain due to historic value.
Signals can either be placed nearside – between the stop line and the kerbline of the intersecting road – or farside – on the opposite side of the junction. In European countries, signals are often placed on the nearside. In the UK, at least two signal heads are required (known as the primary and secondary heads), one of which is normally nearside and the other of which could be nearside or farside. In the US, signals are normally located farside, though in some states, nearside signals are also used. Nearside signals can be beneficial to road safety, as drivers have more time to see a red light and are less likely to encroach on pedestrian crossings.
Effects
Drivers spend on average around 2% of journey time passing through signalised junctions. Traffic lights can increase the traffic capacity at intersections and reduce delay for side road traffic, but can also result in increased delay for main road traffic. Hans Monderman, the innovative Dutch traffic engineer, and pioneer of shared space schemes, was sceptical of their role, and is quoted as having said of them: "We only want traffic lights where they are useful and I haven't found anywhere where they are useful yet."
A World Economic Forum study found that signalised junctions are linked to higher rates of localised air pollution. Drivers accelerate and stop frequently at lights and as such peak particle concentration can be around 29 times higher than during free-flow conditions. The WEF recommends that traffic authorities synchronise traffic signals, consider alternative traffic management systems and consider placing traffic lights away from residential areas, schools, and hospitals.
The separation of conflicting streams of traffic in time can reduce the chances of right-angle collisions by turning traffic and cross traffic, but they can increase the frequency of rear-end crashes by up to 50%. Since right-angled and turn-against-traffic collisions are more likely to result in injuries, this is often an acceptable trade-off. They can also adversely affect the safety of bicycle and pedestrian traffic. Between 1979 and 1988, the city of Philadelphia, Pennsylvania, removed signals at 199 intersections that were not warranted. On average, the intersections had 24% fewer crashes after the unwarranted signals were removed. The traffic lights had been erected in the 1960s because of since-resolved protests over traffic. By 1992, over 800 traffic lights had been removed at 426 intersections, and the number of crashes at these intersections dropped by 60%.
Justification
The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. You may improve this section, discuss the issue on the talk page, or create a new section, as appropriate. (December 2010) (Learn how and when to remove this message) |
Criteria have been developed to help ensure that new traffic lights are installed only where they will do more good than harm and to justify the removal of existing traffic lights where they are not warranted. They are most often placed on arterial roads at intersections with either another arterial road or a collector road, or on an expressway where an interchange is not warranted. In some situations, traffic signals can also be found on collector roads in busy settings.
The International Municipal Signal Association provides input as to standards concerning traffic signals and control devices. One example is the input the association provided for the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD is issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT).
In the United States, the criteria for installation of a traffic control signal are prescribed by the Manual on Uniform Traffic Control Devices (MUTCD), which defines the criteria in nine warrants:
- Eight-hour vehicular volume. Traffic volume must exceed prescribed minima for eight hours of an average weekday.
- Four-hour vehicular volume. Traffic volume must exceed prescribed minima for four hours of an average weekday.
- Peak hour volume or delay. This is applied only in unusual cases, such as office parks, industrial complexes, and park and ride lots that attract or discharge large numbers of vehicles in a short time, and for a minimum of one hour of an average weekday. The side road traffic suffers undue delays when entering or crossing the major street.
- Pedestrian volume. If the traffic volume on a major street is so heavy that pedestrians experience excessive delays in attempting to cross it.
- School crossing. If the traffic density at school crossing times exceeds one per minute which is considered to provide too few gaps in the traffic for children to safely cross the street.
- Coordinated signal system. For places where adjacent traffic control signals do not keep traffic grouped together efficiently.
- Crash experience. The volumes in the eight- and four-hour warrants may be reduced if five or more right-angle and cross traffic turn collisions have happened at the intersection in a twelve-month period.
- Roadway network. Installing a traffic control signal at some intersections might be justified to encourage concentration and organization of traffic flow on a roadway network.
- Intersection near a grade crossing. A traffic control signal is often justified at an intersection near a railroad crossing, in order to provide a preemption sequence to allow traffic queued up on the tracks an opportunity to clear the tracks before the train arrives.
In the US, an intersection is usually required to meet one or more of these warrants before a signal is installed. However, meeting one or more warrants does not require the installation of a traffic signal, it only suggests that they may be suitable. It could be that a roundabout would work better. There may be other unconsidered conditions that lead traffic engineers to conclude that a signal is undesirable. For example, it may be decided not to install a signal at an intersection if traffic stopped by it will back up and block another, more heavily trafficked intersection. Also, if a signal meets only the peak hour warrant, the advantages during that time may not outweigh the disadvantages during the rest of the day.
In other contexts
The symbolism of a traffic light (and the meanings of the three primary colours used in traffic lights) are frequently found in many other contexts. Since they are often used as single spots of colour without the context of vertical position, they are typically not comprehensible to up to one in ten males who are colour blind.
Traffic lights have also been used in computer software, such as the macOS user interface, and in pieces of artwork, particularly Traffic Light Tree in London, UK.
Racing
See also: Racing flagsAutomobile racing circuits can also use standard traffic signals to indicate to racing car drivers the status of racing. On an oval track, four sets may be used, two facing a straight-away and two facing the middle of the 180-degree turn between straight-away. Green would indicate racing is underway, while amber would indicate to slow or while following a pace car; red would indicate to stop, probably for emergency reasons.
Scuderia Ferrari, a Formula One racing team, formerly used a traffic light system during their pit stops to signal to their drivers when to leave the pits. The red light was on when the tires were being changed and fuel was being added, amber was on when the tires were changed, and green was on when all work was completed. The system is (usually) completely automatic. However, the system was withdrawn after the 2008 Singapore Grand Prix, due to the fact that it heavily delayed Felipe Massa during the race, when he was in the lead. Usually, the system was automatic, but heavy traffic in the pit lane forced the team to operate it manually. A mechanic accidentally pressed the green light button when the fuel hose was still attached to the car, causing Massa to drive off, towing the fuel hose along. Additionally, Massa drove into the path of Adrian Sutil, earning him a penalty. He finally stopped at the end of the pit lane, forcing Ferrari's mechanics to sprint down the whole of the pit lane to remove the hose. As a result of this, and the penalty he also incurred, Massa finished 13th. Ferrari decided to use a traditional "lollipop" for the remainder of the 2008 season.
Another type of traffic light that is used in racing is the Christmas Tree, which is used in drag racing. The Christmas Tree has six lights: a blue staging light, three amber lights, a green light, and a red light. The blue staging light is divided into two parts: Pre-stage and stage. Sometimes, there are two sets of bulbs on top of each other to represent them. Once a driver is staged at the starting line, then the starter will activate the light to commence racing, which can be done in two ways. If a Pro tree is used, then the three amber lights will flash at the same time. For the Sportsman tree, the amber light will flash from top to bottom. When the green light comes up, the race officially begins but if a driver crosses the line before that happens, then a red light will come up and that will be a foul.
As a rating mechanism
See also: Traffic light rating system and European Union energy labelThe colours red, amber, and green are often used as a simple-to-understand rating system for products and processes. It may be extended by analogy to provide a greater range of intermediate colours, with red and green at the extremes.
In Unicode
In Unicode, the symbol for U+1F6A5 🚥 HORIZONTAL TRAFFIC LIGHT is HORIZONTAL TRAFFIC LIGHT and U+1F6A6 🚦 VERTICAL TRAFFIC LIGHT is VERTICAL TRAFFIC LIGHT.
See also
- Ampelmännchen
- Glossary of road transport terms
- Induction loop
- Lane control lights
- Level crossing
- Railway signal, rail equivalent
- Pedestrian crossing
- Ramp meter
- Stack light, used in industrial process control
- Traffic light coalition
- Traffic light control and coordination
- Traffic-light signalling and operation
- Traffic optimization
- Traffic robots in Kinshasa
- Slow Children At Play
- Smart traffic light
- Yellow trap
Notes
- Not completely correct: a variable speed sign is not solely used for the purpose of slowing the speed of motorists approaching an intersection. They are also used on freeways where the maximum safe speed is dependent on the conditions of the roadway (i.e. weather, falling rocks, risk of wildlife, etc.), such as in British Columbia, Canada.
- The Barnes Dance is named after an American traffic engineer, Henry A. Barnes. Barnes did not claim to have invented the system but was a strong advocate of it, having observed the difficulties his daughter faced crossing the road to get to school.
- These are typically older signals. There are many examples in Houston, Texas, of this. Suspended lights constructed so that a single source simultaneously illuminates all four directions always have this characteristic: Red (in two directions) and green (in the two cross directions) with Red-Yellow-Green sequence on two sides and Green-Yellow-Red sequence on the cross sides
References
- "robot – definition of robot in English – Oxford Dictionaries". Oxford Dictionaries – English. Archived from the original on 14 August 2018.
- "see robot – definition of robot in Dictionary of South African English". Editor's Note: The origin of 'robot' used as 'traffic light' is from the English translation of the play R.U.R. by Karel Čapek which debuted in England in 1923 which introduced the term 'robot' to an English audience. For a short time in England it was fashionable to use 'robot' for 'traffic light' from the late 1920s, when traffic lights were being installed in England. This usage travelled to South Africa in the early 1930s, when they had their first traffic lights installed, and where it continues to be used almost 90 years later, while 'robot' for 'traffic light' fell out of usage in England. See Foster, B. 1970. The changing English language. Harmondsworth, Middlesex: Penguin.
- McShane, Clay (March 1999). "The Origins and Globalization of Traffic Control Signals" (PDF). Journal of Urban History. 25 (3): 379–404. doi:10.1177/009614429902500304. S2CID 110125733. Retrieved 27 October 2019.
- ^ Convention on Road Signs and Signals of 1968; European Agreement Supplementing the Convention; and, Protocol on Road Markings, Additional to the European Agreement : (2006 consolidated versions). New York: United Nations. Economic Commission for Europe. Transport Division. 2007. ISBN 978-92-1-139128-2. OCLC 227191711.
- see Variations in traffic light operation
- Thames Leisure. "12 Amazing Facts About London". Archived from the original on 7 January 2017. Retrieved 25 January 2017.
- ^ Sessions (1971), p. 141.
- Sessions (1971), p. 22.
- Bellis, Mary (5 February 1952). "The History of Roads and Asphalt". theinventors.org.
- Sessions (1971), pp. 27–28.
- "New Traffic Signal Installed". The Motorist. Ken Pub. Co: 28–29. August 1914.
- Clark, Larry (Fall 2019). "Traffic signals: A brief history". Washington State Magazine. Washington State University. Retrieved 19 December 2021.
- ^ Moyer, Sheldon (March 1947). "Mr. 'Trafficlight'". Motor News. Archived from the original on 13 September 2023 – via large.stanford.edu.
- ^ "First Tri-Color, Four-Directional Traffic Signal, 1920". The Henry Ford. Archived from the original on 12 March 2024.
- Pollard, Justin (September 2008). "The Eccentric Engineer: The History of Traffic Lights Is Full of Twists and Turns". Engineering and Technology. 3 (15): 93. doi:10.1049/et:20081518 (inactive 7 December 2024) – via IET Digital Library.
{{cite journal}}
: CS1 maint: DOI inactive as of December 2024 (link) - McShane (1999), p. 385.
- "US Patent: US1475024A 'Traffic signal' (1923)". patents.google.
- Sessions (1971), p. 143.
- ^ Traffic Signs Manual – Chapter 6: Traffic Control. Department for Transport, Department for Infrastructure (Northern Ireland), Transport Scotland and Welsh Government. Accessed: 18 December 2021.
- "Flashing Yellow Arrow Traffic Signals – Traffic Engineering – MnDOT". www.dot.state.mn.us. Retrieved 18 December 2021.
- "MUTCD 11th Edition - Part 4" (PDF). Federal Highway Administration. Retrieved 13 December 2024.
- "RoadSense for Drivers – Signs, Signals and Road Markings" (PDF). Archived from the original (PDF) on 22 October 2013. Accessed: 25 March 2014
- Ontario Traffic Manual Book 12: Traffic Signals. Ministry of Transportation of Ontario. 2012. p. 55.
- The Kyunghyang Shinmun, ed. (14 May 2024). "Supreme Court rules that driver should stop when yellow light turns on even if car is expected to stop in intersection".
- SBS, ed. (22 May 2024). '갈까 말까' 딜레마존…"안 겪어보면 몰라" 판결에 분통 [사실은] (in Korean).
- "The Supreme Court ruled that if a yellow light is turned on at the traffic light just before enterin.. - MK". Maeil Business Newspaper. 13 May 2024. Retrieved 11 October 2024.
- https://www.itf-oecd.org/sites/default/files/docs/halving-road-deaths-korea.pdf
- "Frequently Asked Questions – Part 4 Highway Traffic Signals – FHWA MUTCD". Federal Highway Administration (FHWA). Retrieved 18 December 2021.
- "The Flashing Yellow Arrow and the Yellow Trap". 7 January 2015. Retrieved 3 April 2019.
- "FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4D". Federal Highway Administration (FHWA). Retrieved 19 May 2009.
- "FHWA – MUTCD – 2003 Edition Revision 1 Chapter 2C". Federal Highway Administration (FHWA). Retrieved 19 May 2009.
- ^ 2009. Manual on Uniform Traffic Control Devices for Streets and Highways: Chapter 4. US Federal Highway Administration. URL Accessed: 7 January 2022.
- "Section 4L.02 Intersection Control Beacon". Manual on Uniform Traffic Control Devices. Federal Highway Administration. 2009.
- "Traffic Signals". Carrollton Texas. Archived from the original on 13 January 2010. Retrieved 12 July 2014.
- Backhaus, Peter (25 February 2013). "The Japanese traffic light blues: Stop on red, go on what". The Japan Times. Retrieved 14 July 2017.
- "The Traffic Signs Regulations and General Directions 2016". legislation.gov.uk. The National Archives. 2016. Retrieved 14 July 2017.
- Forschungsgesellschaft für Straßen- und Verkehrswesen (2000). Begriffsbestimmungen, Teil: Verkehrsplanung, Straßenentwurf und Straßenbetrieb. FGSV Verlag. p. 81.
- Andreas Richter (2005). Geschwindigkeitsvorgabe an Lichtsignalanlagen. DUV. pp. 33–34. ISBN 3-8244-0828-7.
- "Pedestrian Signals". SF Better Streets. 25 December 2011. Retrieved 18 December 2021.
- Maoate-Cox, Daniela (11 September 2014). "Kate Sheppard lights encourage voting". Radio New Zealand. Retrieved 20 September 2016.
- Nicoll, Jared (8 August 2016). "Carmen Rupe lighting up Wellington streets once again". Stuff.co.nz. Retrieved 20 September 2016.
- Melican, Brian (28 January 2014). "Why the green man is king in Germany".
- "Section 4D-1 Pedestrian Signal Indications". Manual on Uniform Traffic Control Devices, Chapter 4D (PDF). 1986 revision (6th ed.). Federal Highway Administration. 1978. p. 4D-1. See also Figure 4-3 "Pedestrian signal face designs", p. 4D-3.
- "Arrêté du 21 avril 2023 portant expérimentation d'une phase jaune de temps de dégagement piéton sur des feux piétons".
- "New traffic signals make it safer for pedestrians". USA Today. Retrieved 19 December 2021.
- "Leading Pedestrian Interval". City of Toronto. 17 November 2017. Retrieved 19 December 2021.
- ^ Schmitz, Jacob (1 July 2011). "The Effects of Pedestrian Countdown Timers on Safety and Efficiency of Operations at Signalized Intersections". Civil and Environmental Engineering Theses, Dissertations, and Student Research.
- Kłos, Marcin Jacek; Sobota, Aleksander; Żochowska, Renata; Karoń, Grzegorz (11 September 2020). "Effects of countdown timers on traffic safety at signalized intersections". Transactions on Transport Sciences. 11 (2): 19–27. doi:10.5507/tots.2020.010. ISSN 1802-971X. S2CID 225185972.
- "Smartphone texting linked to compromised pedestrian safety". ScienceDaily. Retrieved 8 June 2024.
- Broom, Douglas (1 November 2021). "Zombie traffic lights' are saving the lives of smartphone users - here's how". World Economic Forum. Retrieved 8 June 2024.
- Park, Miles (29 June 2014). "Sublime design: the PB/5 pedestrian button". The Conversation. Retrieved 19 December 2020.
- Types of Pedestrian Crossing in the UK. 2pass.co.uk.
- "横断歩道、減る「通りゃんせ」 音響信号「ピヨピヨ」化:朝日新聞デジタル". 朝日新聞デジタル (in Japanese). Archived from the original on 6 November 2020. Retrieved 1 September 2020.
- "Advanced Stop Line | Cycling Embassy of Great Britain". www.cycling-embassy.org.uk. Retrieved 19 December 2021.
- ^ Dutch, Bicycle (3 April 2011), "Junction design, the Dutch – cycle-friendly – way [120]", YouTube, retrieved 18 December 2021
- "Manchester opens UK's first CYCLOPS cycling junction". Intelligent Transport. Retrieved 18 December 2021.
- "What is a Toucan crossing?". Auto Express. Retrieved 19 December 2021.
- "8C". 2009 Manual on Uniform Traffic Control Devices (Report). Rev. 3. United States Department of Transportation, Federal Highway Administration. July 2022. Retrieved 24 December 2024.
- "Publication on traffic lights the from the Swedish Transport Administration" (PDF). Archived from the original (PDF) on 23 September 2016. Retrieved 25 August 2011.
- (in Dutch) RVV 1990 artikel 70 Official regulation of traffic rules and traffic signs
- "Emergency vehicle traffic signal preemption system". United States Patent and Trademark Office. Archived from the original on 21 December 2016. Retrieved 7 October 2005.
- "FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4F". dot.gov.
- "Emergency Vehicles at Red Signal or Stop Sign". Ohio Laws and Rules. Retrieved 22 July 2014.
- "Emergency Service and Vehicles". Virginia General Assembly. Retrieved 22 July 2014.
- Robinson, Larry. "Traffic Signal Progression". Retrieved 22 May 2014.
- "Going Nowhere Fast? Smart Traffic Lights Can Help Ease Gridlock". HowStuffWorks. 18 May 2022. Retrieved 4 February 2023.
- Traffic Signals 101 Archived 28 February 2021 at the Wayback Machine, Minnesota Department of Transportation, 2006
- "Traffic Signal Design Terminology". www.traffic-signal-design.com. Retrieved 2 October 2022.
- DfT Traffic Advisory Leaflet 1/06, Part 4 – https://tsrgd.co.uk/pdf/tal/2006/tal-1-06_4.pdf
- "How does a traffic light detect that a car has pulled up and is waiting for the light to change?". Howstuffworks. April 2000. Retrieved 7 January 2021.
- "Motorcycles And Stoplights". Motorcycle Assistant.
- "Yellow lights shorter in Chicago". Chicago Tribune. 22 March 2010. Retrieved 4 February 2023.
- "Signalized Intersections Informational Guide" (PDF).
- ^ "FHWA – MUTCD – 2003 Edition Revision 1 Chapter 4J". Federal Highway Administration (FHWA). Retrieved 19 December 2021.
- "Which European country has the strictest driving penalties?". Zutobi Drivers Ed. 8 April 2021. Retrieved 19 December 2021.
- "2019 Traffic Safety Culture Index". AAA Foundation. 11 June 2020. Retrieved 19 December 2021.
- "How to Prevent Red Light Runners". Western Systems. 25 March 2021. Retrieved 19 December 2021.
- Michael Knight (30 December 1979). "For Boston Drivers It's Turn Right on Red and Full Speed Ahead". The New York Times. Retrieved 11 August 2022.
- 42 U.S.C. § 6322
- "The Green Arrow". German Pedestrians' Association (FUSS e.V.). Archived from the original on 28 January 2021. Retrieved 28 January 2021.
- "Pravilnik o prometni signalizaciji in prometni opremi na javnih cestah". Uradni List RS (in Slovenian). Služba Vlade RS za zakonodajo: 56. 2016. Retrieved 25 August 2021.
2444 — Vožnja desno ob rdeči luči na semaforju
- Arrêté du 24 novembre 1967 relatif à la signalisation des routes et des autoroutes – Article 7. "Arrêté du 24 novembre 1967 relatif à la signalisation des routes et des autoroutes – Article 7 | Legifrance". Archived from the original on 12 April 2016. Retrieved 2 October 2015.
- "The Highway Code: Using the road (rule 177)". Retrieved 26 June 2015.
- "LED traffic lights could pose winter driving risk". CTV. 5 October 2011. Retrieved 5 October 2011.
- Elizabeth Leamy; Vanessa Weber (4 January 2010). "LED Traffic Lights Unusual, Potentially Deadly Winter Problem". ABC News.
- Marmarelli, Beth (22 June 2011). "Engineering Team Develops Device to Aid LED Traffic Signals in Inclement Weather & Places Overall in Campus's Senior Design Competition". University of Michigan. Archived from the original on 13 April 2012. Retrieved 22 June 2011.
- Hankscraft Inc. (11 October 2012). "Patent application title: Traffic Light Heater". Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942. United States Patent Office. Retrieved 11 October 2012.
- "Intelight ESB Traffic Signal Head". intelight-its.com. Archived from the original on 8 August 2014. Retrieved 21 June 2013.
- The Recorder, Village of Canajoharie to permanently move historic dummy light out of Wagner Square, Shenandoah Briere, August 10, 2022 Archived 10 July 2023 at the Wayback Machine, Retrieved Jul. 10, 2023.
- ^ Buckholz, Jeffrey W. Traffic Signal Supports, Indications and Signing (PDF). Woodcliff Lake, NJ: CED Engineering.
- "A Dummy Forever!". Croton Friends of History. Retrieved 18 December 2021.
- ^ "Near Side Signals: Thinking Outside the Pedestrian Box". Streets.mn. 30 April 2021. Retrieved 4 February 2023.
- ^ "Why traffic lights are pollution hotspots". World Economic Forum. Retrieved 19 December 2021.
- "Traffic Signals" (PDF). Institute of Transportation Engineers. September 2007. Archived from the original (PDF) on 27 March 2009. Retrieved 1 April 2009.
- David Millward (4 November 2006). "Is this the end of the road for traffic lights?". The Daily Telegraph. Retrieved 1 April 2009.
- ^ National Cooperative Highway Research Program, Crash Reduction Factors for Traffic Engineering and Intelligent Transportation System (ITS) Improvements: State-of-Knowledge Report, November 2005, Table 3
- "Archives - Philly.com". The Philadelphia Inquirer. Archived from the original on 4 April 2015.
- "International Municipal Signal Association", Misplaced Pages, 23 October 2021, retrieved 8 July 2023
- "Manual on Uniform Traffic Control Devices", Misplaced Pages, 8 July 2023, retrieved 8 July 2023
- Section 4C. Manual on Uniform Traffic Control Devices (2009 Edition). Mutcd.fhwa.dot.gov.
- "Traffic Light Song". YouTube. 16 June 2017. Archived from the original on 11 December 2021.
Citations
- City of Beacon. Canajoharie, New York: Credits. Retrieved 30 September 2008.
- Croton-on-Hudson Historical Society. Canajoharie, New York: Credits. Retrieved 30 September 2008.
- Villages of Canajoharie & Palatine Bridge. Canajoharie, New York: Credits. Retrieved 30 September 2008.
- Sessions, Gordon M. (1971). Traffic devices: historical aspects thereof. Washington: Institute of Traffic Engineers. OCLC 278619.
- Woods, Arthur (April 1916). "Keeping City Traffic Moving: One of the Most Difficult of All City Problems, And The New Methods Which Have Been Devised To Solve It". The World's Work: A History of Our Time. XXXI. Doubleday, Page & Company: 621–532. Retrieved 4 August 2009.
External links
- FHWA Arterial Management Website, latest information on traffic signal operations
- Animations of various US signal phasings Archived 17 May 2013 at the Wayback Machine
- SCATS – Sydney Coordinated Adaptive Traffic System
- Safety Evaluation of Converting Traffic Signals from Incandescent to Light-emitting Diodes: Summary Report Federal Highway Administration
- Safety Evaluation of Discontinuing Late-night Flash Operations at Signalized Intersections: Summary Report Federal Highway Administration
- Traffic signals, 1922, digitized NYPD photograph from the Lloyd Sealy Library Digital Collections
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