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– March 2006 – April 18th 2006

SEPARATE PAGE FOR DISCUSSION OF PRT IN GENERAL

Improving the Page

What does "improve the page" mean?Avidor 15:58, 18 April 2006 (UTC)

I would improve the page by having the definition of PRT conform to the description in this recent, neutral study from Portland The study says PRT is only a concept. They also give it failing grades.Avidor 21:52, 20 April 2006 (UTC)

That study can't even get past the usual misconception about capacity and PRT vehicle size. That plus not liking PRT fleet size misses a basic feature of the PRT service concept. The belief that a large complex network would be needed treats PRT as somehow not able to be intermodal. And $200 million a mile? That's a light rail cost estimate. Rather than being neutral, I'd characterize this section of the report as not fully informed. -21apr06, 1:40a CDT

See a pattern here? I cite two independent studies, the 2001 OKI Report and this current Portland study and PRT proponents (anonymous) provide an excuse for dismissing the studys' findings. So from what source should Misplaced Pages editors use to determine facts in this article? Should we use government studies that have been conducted in an open and transparent manner with input from citizens and transportation professionals or should Misplaced Pages use promotional websites and anonymous sources? I again recommend that the introduction to the PRT page be re-written to conform to the definition of PRT in Ŗthe Portland screening report on page A-13 of this PDF file. It is concise, easy to read and is lacking in promotional fancruft.Avidor 13:50, 21 April 2006 (UTC)

The pattern is that you continue to cite the OKI study even though a dissenting report identified serious flaws in it--a fact, not an "excuse", just as the above-noted Portland errors are facts too. The pattern is that you continue to pretend the dissent and those flaws do not exist. The pattern is that you want to portray PRT as you want it to be, not as it really would be. -21apr06, 1:41p CDT

...based on rosy, optimistic, "faith-based" assumptions, not real-world facts.Avidor 22:12, 21 April 2006 (UTC)

This is a discussion about a concept that a lot of people would like to try, and which credible, unconnected authorities believe is feasible. For every OKI report or Portland study which claims to find PRT has problems, there is an EU Commission, German transport agency or Swedish Royal Institute that validates the concept. To return to The Pattern, you only give credence to the reports (even with identifiable flaws) that find against PRT, and ignore all the others. Rosy, optimistic, "faith based"? You have blinders too. It would help your credibility if you could admit to ever having made an error of fact (how about the remark about pods swinging in the wind?). It would help your credibility to acknowledge that there are flaws in OKI. This is not life & death. This is a discussion about technology and innovation. -21apr06, 6:11p CDT

That's a good idea....how about an....

Independent Evaluation of PRT Section

I'd include a link to the OKI study and the Portland study and the proponents can add their favorite independent studies...good idea!!!Avidor 20:28, 22 April 2006 (UTC)

No, because simply calling OKI and Portland "independent" does not remove their flaws. Adding such a section would put this page on the road back to the we say/they say era prior to JZG's arrival. Already we have a section that lists links to flawed skepticism, and I still haven't seen a good explanation of why those are allowed to remain as if they are unimpeachable. We should continue with the current effort to make this article about the PRT concept as it would be developed by the people who are designing the various versions--not what the opponents imagine or claim PRT would be like. -24apr06, 12:15p CDT

Cost and ridership section

Avidor removed this section, I assume because of the 85-95% number. I believe this number is reasonable, but I can't find sources for it. It seems like common sense to me, given that buses and trains inherently have extremely low utilization during non-busy times, which would tend to offset the higher utilizations during rush hours. I'd be curious to know what Transit Guest and LDemery think about this number (maybe they can provide a more accurate number, with sources?)

In any event, I've attempted to rewrite the section to better explain the point. I believe that every statement there (except perhaps the 85-95% number) is completely factual and mathematically correct. If not, please address your concerns here. A Transportation Enthusiast 22:01, 7 April 2006 (UTC)

Assumptions aren't facts. It's your job to do the research to back your claims. 85-95%? prove it.Avidor 02:00, 8 April 2006 (UTC)

I don't know where the original 85-95% claim came from, so I've rewritten the section with that line removed. A Transportation Enthusiast 04:41, 8 April 2006 (UTC)

OK, this is what I don't understand, Avidor. You were concerned about the veracity of the 85-95% number, so you removed the entire section containing that number. Fine. I made the effort to rewrite the section to make the point more clearly. I kept the 85-95% number in with a request (here on the talk page) for clarification from other users, especially Transit Guest and LDemery who seem to have a handle on transit stats. No matter though, because a little while later you once again removed the entire section, apparently not having read my plea here for reasoned debate on the contents of this section. So, fine. I reworded the section once again, this time removing all reference to the 85-95% number and replacing it with hard facts. But, once again, this apparently wasn't good enough even for discussion, because you went in and deleted the whole section for the third time, without a word of discussion here! What is the problem now? Every single word in that section is factual and neutrally presented! Why do you repeatedly remove it?

I've reverted the deletion. If you have a problem with this section, please discuss it here. A Transportation Enthusiast 14:36, 8 April 2006 (UTC)

It is not factual. Every transportation system has to have excess capacity for unanticipated ridership including Anderson's Taxi 2000 PRT design. This section is just the usual U.S.-centric transit bashing that suggests that rail and bus everywhere in the world are the same as in the U.S.. Empty buses and trains may be something you've seen in North Carolina but you cannot say the same of Zurich, Tokyo, New York, London etc. Encyclopedias should not have biased assumptions in place of facts.Avidor 15:43, 8 April 2006 (UTC)

No, you are missing the point! We've been over this before: buses and trains have fixed operational overhead regardless of demand. PRT has overhead that is proportional to demand. Even if that overhead includes empty vehicle movement (i.e. "1/3 empty vehicles"), that overhead is still proportional to demand! I already explained this above on this talk page.

The argument in this section is basically: round-the clock, high-frequency, scheduled transit is impractical (i.e. not cost effective) in almost every market in the country, because the costs of service availability are high regardless of whether people are using the system or not. PRT can provide round-the-clock service because it is demand based and therefore incurs no added costs for being available during off hours. This is the point, it's completely valid, completely factual, and I'm putting it back in. Do not remove it again unless you have a specific complaint about one of the assertions. A Transportation Enthusiast 16:05, 8 April 2006 (UTC)

1. PRT has a fixed overhead limit: the number of cars. Regardless of demand, there are going to be a fixed number of cars on the system. (Obviously, like buses or rail rolling stock, it may increase if total demand rises over time.) Many of the cars may not be in motion, either parked at stations waiting for users or stored at storage yards or maintenance facilities, but they are still there, and they have to be maintained.

2. Simiarly, PRT does have substantial fixed costs: maintenance of guideways, switches, and vehicles, and costs for staffing of control/monitoring centers, as well as normal management and administrative costs. If you offer all-night service, then you need to staff your maintenance and control centers all night, as well as providing system-wide security at night. All-night operations means that some maintenance and cleaning will be done at night, and emergency/maintenance crews (maybe just a few guys in trucks with cherry-picker lift-baskets to rescue stranded riders) will be needed. Most rail transit systems do heavy track and station maintenance at night when systems are not running or when demand is low and trains can be detoured on single-tracks - PRT would be the same.

3.Buses and train do scale in response to demand. Frequency of service changes during the day, increasing during rush hour and declinging (or suspending) over night. It's true that these changes are in response to broad patterns of aggregate demand, and not specific individual demand, but its slao still true that transit agencies try to match their service frequency (and use of longer trains or larger articulated buses) to demand.

4. Buses and trains can scale up much faster to predicted large surges in demand, such as running special trains and buses for sporting events or parades, or scaling back service on holidays.

5. Low-capacity is not a serious problem for traditional transit, per se. Some buses and trains may run at very low capacity at some times, but if such patterns persist then it is likely that either (a) transit agencies will reduce or eliminate the service, or (b) the agencies feel that the offering a particular under-utilized route (esp. buses) actually enhances overall service by maintaining demand for transit and flexibility for riders. That is, if low-demand routes were cut, regular transit-reliant users would find the total utility of the system greatly reduced and would turn to private cars, eventually reducing their transit usage of both low-demand AND high-demand routes.

6. "PRT has overhead that is proportional to demand" is trivial. All transit has overhead that is proportional. Increasing rail and bus service means hiring more drivers, mechanics, security, maintenance, dispatchers, and other personnel. Increasing PRT service (i.e. more vehicles or guideways) would require hiring more vehicle mechanics, track and stations maintenance crews, security, monitors (overseeing the system at the central control center) and other personnel. All PRT does is remove the drivers. Other vehicle and operations costs will scale just like rail or buses. And, of course, real-world experience indicates that some of the cost savings of automation will be offset by additional monitoring and maintenance (if not all the costs - or more!). -- Transit Guest 15:33, 10 April 2006 (UTC)

In respose to your points:

• "PRT has a fixed overhead limit: the number of cars" - this is directly analogous to the number of buses and trains needed to accomodate maximum load. However, the point is, in almost every city, it is impractical to run those buses and trains at maximum service frequency 24 hours a day. PRT, on the other hand, can be available 24 hours a day with little or no cost implications.
• "If you offer all-night service, then you need to staff your maintenance and control centers all night, as well as providing system-wide security at night" - maintaining a minimal staff for security and control is hardly comparable to maintaining a full complement of drivers, etc, that would be required to provide the same level of service from trains or buses. In fact, the low usage would likely require a proportionately lower staff on hand in control and monitoring.
• "maybe just a few guys in trucks with cherry-picker lift-baskets to rescue stranded riders" - oh come on, Transit Guest. Are we having a serious discussion here or are we going to start hurling propaganda? I can just as easily say something inflammatory, like "light rail has maybe a few ambulances on call to handle derailed trains..." You know as well as I that no system would be so unreliable as to require a cherry-picker on standby.
• "Buses and train do scale in response to demand." - and the article clearly states that scheduled-transit planners will adjust schedules based on anticipated demand. But this is much different than providing immediate, on-demand service. And, buses and trains stop running entirely at night, in many (most) low-demand cities.
• "Buses and trains can scale up much faster to predicted large surges in demand, such as running special trains and buses for sporting events or parades" - if a PRT system is built to handle large crowds (i.e. high station density, large stations at sports venues), and the guideways can handle the capacity, then it can scale up just as well. It's just a matter of throughput: if PRT can push the same amount of maximum capacity as LRT, then it's just a matter of loading people into the pods - and that can be achieved by having a larger amount of small stations scattered in an area, rather than one huge station that serves that whole area.
• "...or scaling back service on holidays." - but that's the whole point. PRT doesn't have to scale back on holidays, because it doesn't have to pay a full staff of drivers double-time to drive the vehicles. But what about the poor souls who happen to be travelling on a holiday? If scheduled transit is not available, they're out of luck.
• "That is, if low-demand routes were cut, regular transit-reliant users would find the total utility of the system greatly reduced and would turn to private cars, eventually reducing their transit usage of both low-demand AND high-demand routes." - but this illustrates the very benefit of PRT in a nutshell! PRT can provide service at all times, at all locations with little or no cost implication. There's no service-cost tradeoff with PRT. Users don't have to worry about schedules, or about reduced holiday service, or about their routes being scaled back or eliminated due to low usage. They don't have to worry about these things, because with PRT there is no reason to cut service. They can leave their automobiles at home during the day, at night, on holidays, with complete confidence that PRT will always be available at all locations. What better way to encourage people to leave their cars behind?
• "All transit has overhead that is proportional." - then why do trains stop running at night? If the operational overhead of running trains were proportional to demand, then there would be no reason to reduce or eliminate service during off-peak hours.
• "All PRT does is remove the drivers." - not true. PRT vehicles will only move in response to demand, so energy costs are reduced. How much energy would it take to run buses/trains at regular frequency 24-7? Also, vehicle cleaning/maintenance is minimal for PRT during off hours: if most vehicles are lying idle in stations waiting for riders, they are not getting dirty and are not experiencing wear. Same for guideway wear, and security monitoring, and control -- if the system is mostly idle, why would full staff be necessary?
• "And, of course, real-world experience indicates that some of the cost savings of automation will be offset by additional monitoring and maintenance (if not all the costs - or more!)" - well, let's compare apples to apples. You are comparing 24 hour, on-demand service to all locations (PRT) with schedule-based service that may run at frequencies of once-per-hour or less, or not at all during low demand times (buses, trains). What would be the overhead of trains running the same level of service as PRT? In other words, if trains ran at 6-minute headways, 24-7, what would the overhead be? That's the only way to compare the overheads, by comparing the two different modes at the same level of service. (Actually, it's not even the same level of service, because even 6-minute train headways equates to an average 3-minute wait for passengers, whereas PRT would provide immediate service with now wait. But I'll concede that a 3-minute wait is close enough).

A Transportation Enthusiast 16:51, 10 April 2006 (UTC)

Maybe this will help settle the "empty"-ness part of this argument:

• "In urbanized areas, rail's 5.8 cents average operating cost per seat mile and bus's 5.9 cents are lower than auto's 7.8 cents. But this potential cost advantage is not realized in practice because bus and rail typically operate with a great deal of excess capacity. In our sample, rail's average load factor is 17.6 percent and bus's is 14.3 percent. Auto's average load factor, based on an average vehicle occupancy of 1.5 people and an average vehicle capacity of 4 people, is 37.5 percent. Thus, auto's 21 cents average operating cost per passenger mile is considerably below rail's 37 cents and bus's 44 cents."

Thus, rail is 82.4% un-loaded, buses 85.7% un-loaded.

references are in the original article:

Clifford Winston, Chad Shirley

Alternate Route: Toward Efficient Urban Transportation (1998)

Brookings Press

brookings.nap.edu/books/0815793812/html/25.html#pagetop

-08apr06 3:40 CDT

Well, that auto number was from DoT in 1997. More recent per-passenger-mile numbers for rail were cited above by me. For auto, AAA (the American Automobile Associate) calculates the average per-mile costs for vehicle ownership in 2005 were 52.2 cents per mile. Even with ridership of 1.5 occupants, that's still 34.8 cents per passenger mile - well above many rail O&M costs. Of course, that is only the direct consumer cost for autos, not the total public cost of auto travel. Apples and oranges, again... -- Transit Guest 15:33, 10 April 2006 (UTC)

Do you have any background on why DoT and AAA's numbers are so far apart? A 62% difference in measurements taken 8 years apart seems larger than could be explained by normal margins of error, or even gas price increases. I wonder if AAA has an incentive to make the cost look as high as possible, so people will be more likely to purchase their services. -10apr06 12:28 CDT

I'd have thought that, as an organization and advocacy group for auto users, AAA would want to make auto-ownership look less expensive - and thus superior to public transit. Go figure.

As for costs, gas prices more than doubled from 1997 to 2004, so the increases aren't out of line. Insurance costs also rose faster than inflation, which alone was over 20% (aggregate) for the period.

PRT Operating costs

My POV, but I believe that "real-world" PRT operating costs (and therefore "cost recovery") will remain a matter of pure and fanciful speculation until such a system gets built and accumulates an actual record of public service.

Contrary to what many people think, it isn't "vehicle occupancy" that hikes transit operating costs. It's the fact that transit is about the most labor-intensive major "industry" there is - and labor, as we know, ain't cheap.

As for "cost recovery," it is possible to make money running a transit service - even today - and even if your service isn't particularly "cost-efficient." The trick is to charge a higher fare per mile than it costs you to operate. Good examples are the Seattle Monorail and several private-sector streetcar operators in Japan.

Certain "techie" types not familiar with the "real world" of transit operations dispute this vigorously - but:

It is now clear from experience overseas that the advantages of automated (aka "driverless") operation of metros and AGT lines do "not" include lower operating costs.

I've read some good "common-sense" editorializing on this subject - e.g. the cost of labor goes up over time, but the cost of computer hardware and software goes down. Sounds reasonable, but things have not worked out that way in the "real world."

The underlying problem - well known after more than 25 years of experience with driverless metros and AGTs - is that the very high cost of the skilled labor needed for systems operation and servicing offsets any savings from running trains without drivers.

Yes there are advantages to driverless operation, and these justify the extra investment (at least the French think so) - just don't expect to save any money from lower operating costs.

Can PRT avoid this problem - which did not become apparent until driverless systems were actually built and "proven" in real-world service? Maybe, maybe not, but quite frankly, I'm skeptical Ldemery 03:40, 8 April 2006 (UTC)

I have two points in response to this:

• First: any system is only as good as its engineering. The existence of previous failures may indicate that automated control is inherently more expensive to operate than conventional transit systems. Or, it may just be that previous systems suffered from their own design and/or engineering mistakes. Personally, I've seen not seen evidence either way. I think it's an open question. Certainly, previous failures will increase skepticism of future designs, but I also believe that newer designs should be judged on their own merit - perhaps with a more critical eye, but with no preconceived notions of infeasibility.
• Second: my impression is that most automated systems in operation today are relatively small. It seems to me that small systems would suffer greater skilled labor overhead than larger systems. For example, the cost of skilled positions (i.e. computer systems administrators) would be less significant when spread out over a larger system budget. Of course, I don't have evidence to support any of this... just my impression.

Basically, it's speculation until a PRT system is built (even then, it might not be answered; if that PRT system fails due to bad design, we don't know any more than we know today. It's much more difficult to prove infeasibility...). So, because of the inherent uncertainty of operating costs, I think it's appropriate that both sides are represented: the pro claim of reduced operating costs, and the anti claim that existing automated systems have not had lower costs. A Transportation Enthusiast 05:07, 8 April 2006 (UTC)

We don't know about costs, but claims can be made as long as they are substantiated and assumptions documented. What we do know though, is that the Dockland Light Railway, which has driverless trains, is the most reliable train service in London - a good model for PRT systems. Stephen B Streater 09:55, 8 April 2006 (UTC)

Info from PRT Websites

Deleting this part

No archive, check Label: "Deleted 'info from PRT websites' " in history. Avidor, don't clutter this talk page with quotes from other people. At LEAST make paragraphs out of those numerous sentences, instead of stringing line after line into a page of text that should be a small paragraph. Fresheneesz 02:44, 13 April 2006 (UTC)

Uni-directional or Bi-directional Guideways, Cost, and Capacity

"Bidirectional service is normally simulated by moving vehicles around the block. Most PRT systems are designed to operate in a network. Traffic is automatically diverted by central controls, so heavily trafficked corridors do not exist, and therefore require no additional construction."

This is absurd - you can't just wish away traffic congestion! If you want to dismiss my previous edits about costs and capacity by citing a "network" that magically eliminates all bottlenecks, you need to specify how dense your network is. After all, there's already a very dense transportation network in every city in America - it's called city streets and highways, and it gets clogged every day.

Speaking of roads, why don't I slyly beat all those other gridlocked fools by driving the long way around and entering downtown from a secret back entrance? Because there isn't one! People commute from ALL directions into downtown - and if the highways are full then they're full no matter how many times I go around in a circle. The idea that "heavily trafficked corridors do not exist" is fantasy - such corridors exist because people commute to dense concentrations of jobs in business districts and downtown offices. Radial commute patterns mean that anywhere there's land, there's suburbs. Going "around the block" in a PRT car is pointless because commuters are coming in from the other side as well!

As for bi-directionality, keep in mind that if there's only uni-directional guideways spaced every half mile, then that means that the nearest parallel guideway is a mile away. That's not a lot of capacity. Finally, this ignores the information I cited above: that PRT provides less capacity per dollar than rail. It might be faster in some cases, but it can't operate at high volumes and it can't do so with lower costs per passenger mile. -- Transit Guuest 16:47, 10 April 2006 (UTC)

OK, let's attempt to normalize the numbers. From a pure capacity standpoint, assume that a unidirectional PRT "line" can handle 5000 passengers/hr, while grade separated LRT can handle 10000/hr. (And let me qualify this: 5000/hr is pretty conservative for PRT, since 0.5 second headways are technically feasible and a load factor of 1.3 at 7200veh/hr gives capacity close to 10000. But we'll use the more conservative 5000 passengers/hr) This means that four unidirectional PRT lines would be required to match the capacity of one LRT line, right? If grade-separated LRT is $60M, this means that PRT would have to be $15M per mile to provide the same capacity/cost, right? I've seen cost estimates in this range for PRT, though some are over $20M which would make PRT somewhat more expensive than LRT.

But, consider this: even if PRT is somewhat higher, wouldn't the increased service of PRT (point-to-point, on-demand, 24-7 service) be worth the added cost? If PRT can draw 30% or more away from the road system, couldn't the savings in road construction and maintenance offset the added cost of PRT? Personally, I think PRT would be more than worth even 35-50% added costs relative to LRT, given the vastly better service that PRT would provide. But that's just my POV. As far as actual costs of the system itself, it seems that, in general, PRT is no cheaper to construct (and may be more expensive) than LRT. But, again, every situation is different. For Seattle's $200M per mile, you could build a really big PRT network.

A Transportation Enthusiast 17:51, 10 April 2006 (UTC)

5000/hr is conservative? Says who? Let's assume a typical occupancy rate of 1.2 persons per vehicle (in line with other assumptions stated in the article), a recycling rate of "several" (say five) times per hour, and the requisite one third empty for timely resupply. That means you'd need of the order of a thousand vehicles per guideway. Have any of the test systems ever had that kind of number? Has any real-world installation ever approached a thousand operational vehicles? Have any of the proposals which have reached active consideration by city authorities included that kind of number? Has anyone ever compared the cost of running a system like that with the costs of a taxi fleet of comparable capacity?

Yes, absolutely 5000 is conservative. Regulatory agencies may be slow to adopt lower headway standards, because they don't understand the technology, but there exist designs for 0.5 second headways that are safe. The only thing lacking is field testing and operational experience, and that's why most implementations are currently targeting 2 seconds or more. There is absolutely no evidence, technical or otherwise, that 0.5 second headways would be unsafe, and there is mounting evidence that it is workable (see the Berkeley Automated Highway System tests on Buick LeSabres running on specially constructed roadways -- these were full sized automobiles running automated at 60mph with something like 5 feet between them, which equates to sub-half-second headway). Anybody who tells you that half-second headways are imossible on a dedicated guideway either has an agenda (trying to suppress PRT) or does not know what he's talking about. If you want proof that sub-second headways are feasible, take a ride on a rush-hour highway, where disjoint vehicles operated by human beings with very slow reaction times and very high failure rates (i.e. cell phones, coffee spills) regularly run at less than a second headway. Now, of course, highways have a high rate of accidents, but almost all are due to either (a) obstructions in the "guideway" and (b) failures in human judgment or reaction time. Neither of these would apply to PRT. Yes, 5000 is conservative.

As to your other questions, no nobody's run a full scale PRT system. But you are speculating that it wouldn't work. There is a large body of evidence that it would work, including analysis and very in-depth simulations of real systems. You continue to scoff at such things, which is very surprising to me given that you are an engineer, but this is the way the world is designed these days. How do you think something like a new aircraft is designed? They build it on computers, analyze it on computers, test it on computers. Then they build the real thing and take it out for a test flight. You don't hear about new aircraft test flights failing regularly, do you? That's because by the time it's actually built, it's already been through many design and testing iterations. This is where many PRT designs stand today: many iterations of computer-based design and testing that have hardened these designs to the point where the only thing they lack is a field test of a real working system -- something that hasn't happened yet due largely to lack of funds. You continue to scoff at that, JzG, but that's the truth. A Transportation Enthusiast 16:09, 11 April 2006 (UTC)

I'd agree, that IF you could build PRT over existing streets (thus no RoW) for $15m per mile of guideway (including a 3-berth station every 1/2 mile) then yes, you might build part of an LRT capacity system of 4 parallel guideways at $60m per mile. But that is still the upper limit of most LRT projects, such as Los Angeles or Dallas (Seattle being the notable outlier - see below). Compared to systems like Sacramento, San Jose, St. Louis, Denver, and Salt Lake City, which were build or extended for less than $30m per mile, PRT is already over-priced.

Moreover, these PRT cost estimates omit infrastructure like offices, storage yards, control centers, and maintenance facilities, for which RoW would need to be purchased. Those costs are all included in real-world LRT costs, as necessary. Think about that: instead of PRT's speculative costs, you can build light rail networks in many cities as densely as PRT systems promise - for less money! Not as fast, but very convenient nonetheless!

These costs also omit the necessary crossing tracks to allow vehicles to circulate between the guideways and serve all stations on each line. In a 10 mile long system of four parallel tracks (40 miles total), adding the 1.5 mile long crossing routes (crossing all four guideways) at every half mile means 21 such crossing tracks totalling 31.5 miles of additional guideways and stations. That's 75% more guideway and stations - and thus 75% more cost. 10 miles of $25m LRT is $250m; at $60m/mile its $600m. If PRT is $10m/mile, this small system costs $715m; at $15m/mile its over a billion dollars ($1,072m), costing over $100m per mile. That assumes NO right of way costs, for either tracks or stations (unlikely), and you still need to add costs for the aforementioned infrastructure facilities.

To be sure, this hypothetical PRT system would serve passengers at walking distance in a two-mile wide corridor, compared to LRT serving only pedestrian passengers in a half-mile wide corridor. But most LRT system costs also incorporate park-and-ride lots at suburban stations, allowing each station to draw from a much larger area of commuters. Is it less convenient for the commuter? Perhaps. But some people cannot (or choose not to) walk a quarter-mile outdoors, whatever the weather. And driving a half mile is a lot faster than walking a quarter mile, so it may not be any less convenient. PRT could incorporate larger stations and park-and-ride lots, but costs would rise considerably.

And, this system would only occupy one transit corridor, extending ten miles from city center to suburbs (not a great distance in most cities). Nearly all the rides would be along the main direction of the corridor, so there really are only two main lines - giving you only as much capacity as LRT. If the corridor fills up, you've got a build more guideways.

Extending an LRT line to more distant suburbs is usually cheap because the land in the suburbs is cheapera, the stations can be farther apart, and you can build large parking lots. Each additional mile of track drops in cost. That's one problem Seattle is facing - they have to build the really expensive part of the system first and add the cheaper suburban extensions later. SF, DC, LA, Sacramento, and Portland went through the same process. But PRT costs just as much to extend in the burbs - more, actually, because lot sizes and population densities decline but people don't walk any farther, so you need lots of stations. Every additional mile of our hypothetical system of PRT (above) will cost between $70m and $100m - far more than light rail.

Finally, "For Seattle's $200M per mile, you could build a really big PRT network." Actually, no you couldn't. Part of the reason the cost in Seattle is so high is due to the terrain, and also the requirement by local communities and leaders that there be no on-street or elevated tracks downtown - several long stretches HAD to be underground. PRT would have operated under the same restrictions - and it would have required more tunnels. -- Transit Guest 19:22, 10 April 2006 (UTC)

"Think about that: instead of PRT's speculative costs, you can build light rail networks in many cities as densely as PRT systems promise - for less money!"

Costs for PRT will be speculative forever if this chicken vs. egg logic is used to forestall even trying PRT in a real world application. In fact, no one is seriously proposing a first PRT demo on some sort of heavy duty urban corridor, so relax. ULTra's going into an airport, let's see how that works; then we'll get one as a collector-distributor in a suburb or non-CBD urban area. Data will result, from which extrapolations can be made for heavier-duty PRT networks. In the meantime TE and TG, I don't think this thread has a hope of being resolved in favor of one side or another--which must mean that it is valid for the Opposition section. -10apr06 4:00 CDT

"these PRT cost estimates omit infrastructure like offices, storage yards, control centers, and maintenance facilities, for which RoW would need to be purchased." - I think you overestimate the cost of this overhead, especially since these facilities can go just about anywhere with PRT. But I have no hard data to back it up (I'm not a PRT expert by any means) so that's just my opinion.

"instead of PRT's speculative costs, you can build light rail networks in many cities as densely as PRT systems promise - for less money! Not as fast, but very convenient nonetheless!" - I dispute the "very convenient" assertion. If LRT were very convenient then maybe it would draw more than just a few percent from automobiles. About the only places where rail gets a significant cut is cities with VERY mature infrastructure (New York), and even then the cut is not as high as one would hope (what is New York's subway cut? I've heard it's something like 25-30%). I'm not trying to bash rail, but the fact remains that rail and buses are only popular where the automobile is not a viable option, either because people don't own cars (overseas) or because traffic is so bad that the inconveniences of rail are minimized. Scheduled line haul transit will never be convenient enough to compete with automobiles in cities where autos are plentiful and traffic is acceptable.

But the same people who would not accept the inconveniences of rail (walk, wait, board, ride, exit, walk, wait, board, ride, exit, walk) might very well accept the level of service offered by PRT (walk, board, ride, exit, walk). PRT is much faster and much more convenient, and it would appear to be the only type of system with any hope of drawing people away from their cars. Light rail has repeatedly failed to do that, except in situations where cars themselves are very inconvenient.

But I also feel (as the anonymous poster above does) that you and I will never agree on these points, and it's pointless to debate it further. Suffice to say that PRT companies have estimated costs, and those estimates will be inherently speculative until a system is built and the costs can be proven. I think the article reflects that uncertainty, while still representing both sides of the argument. ULTra might give us a better idea in a few years. A Transportation Enthusiast 22:32, 10 April 2006 (UTC)

I think we've actually cleared up quite a bit through the discussion. Such as basic costs per mile, and the fact that, for a given level of capacity, PRT systems will cost two to four times as much as LRT systems to construct and four to six times as much to extend into suburbs - before infrastructure facitilites like storage and maintenance yards or control centers (which typically amounts to 10-25% of the cost of rail projects).

I'm still concerned about the idea that a network magically removes congestion, without any reference to the required density of the network. I also object to the fact that the article still implies that unidirectional PRT is similar in cost and capacity to other modes of transit. I'm re-inserting the text about bi-directional costs.

And, of course, LRT *does* draw people away from cars. show that LRT ridership surged 8.8% for 3Q 2005, at the same time that automobile ridership actually declined! In many cities, ridership grew by more than 10%, and by more than 15% in LA, Sacramento, San Jose, and Tampa. Minneapolis ridership grew by 70%! Commuter and Heavy rail also grew, though not as quickly. -- Transit Guest 13:32, 12 April 2006 (UTC)

No, I don't think much is cleared up, other than that you've reassured yourself that your favorite technology is still superior. You're rigorously applying line-haul assumptions to PRT and declaring victory when the network-based mode can't measure up. You're also ignoring that, whether in a central city or out in the suburbs, additional PRT-miles represents additional geographic coverage, accessibility and therefore potential revenue. You're assuming that the same people would travel up to several miles to access just one LRT line. I'm not surprised that LRT ridership is up--especially if it includes riders of a brand new line--but the question is whether the increase kept pace with the increase in traffic.

I also think some rosy LRT cost assumptions are creeping into the main article: "See light rail for a discussion of its costs, which typically range from nearly zero (for non-grade-separated streetcars) up to US$ 65 million per mile..." Define "nearly zero". Is Seattle computed into the $65 million upper range? I think Seattle needs to be in there rather than dismissed as an anomaly--if theirs is a well-designed well-planned system, then that is a legitimate model for other cities that want rail transit but have topographic challenges. -12apr06 11:40 CDT

I'm not trying to make a round PRT peg fit into a square line-haul hole. Sure, PRT provides network-wide travel - but reducing auto travel outside congested corridors or regions is not a public policy problem, simply because there's already sufficient transportation capacity in the existing road system. Non-congested road travel doesn't need a brand new hundred-million dollar solution. It's the congested routes that need to be addressed. Line-haul (bus or rail) is one solution, but there could just as easily be a linear off-line-station concept, an AGT concept, a PRT concept, or some other transit mode that works in a congested corridor or region. But in any case, that's why I'm looking at corridors. Sure, PRT provides network transit to other places and at other times - but for those places and times, people have cars.

I'd also point out that every time PRT comes up in public policy discourse, it's as an alternative for new or expanded transit programs or highway construction. I.e., in response to concerns that traffic congestion in major commute corridors is getting too burdensome, and that cost-effective solutions are needed. Thus, the terms of any comparison must address the central questions of transit in a congested corridor, and cost. That's the number one concern - and if PRT can't address it as well as rail or bus, that ought to be cleared up.

The problem is that PRT's proposed solution is simply far more expensive than the usual alternatives - even when taken on its own terms! Based on the cost numbers we're talking about, how much would it cost to provide a full PRT network to a mid-sized midwestern US city? For a circle 7.5 miles in radius, its over 8 billion dollars (assuming only $10m per mile!) - and yet most auto commuters on congested highways might travel two or three times that distance, and thus lie far outside the PRT zone! In that same circle, 8 radial light rail lines and a circular connector could be built, at $25m per mile, for less than a third of the PRT cost. And most cities don't need that much public transit! PRT, for all its claims of scalability, is remarkably un-scalable, because you have to build such a huge system before you see any benefits relative to the alternatives.

In suggesting that commuters might travel two miles or more to LRT, I'm not assuming that LRT riders are more dedicated than PRT riders. Rather, LRT costs include features that allow auto commuters to use LRT because LRT incorporates parking lots and garages at stations - features PRT explicitly tries to avoid with a minimal footprint for unobtrusive walkable neighborhood stations. PRT could add surface parking lots or garages and larger stations (perhaps just large parking lots with several small stations dotting the sea of cars!), but that would drive up costs and reduce the convenience that is the main selling point.

As for Seattle, it's more expensive due to topography. But you are omiting the political considerations that rejected on-street and elevated LRT lines and that required major modifications to the city transit tube. A rejection of elevated transit eliminates PRT altogether, so there's no comparison to the $180m/mile figure. And if the city were to allow elevated PRT, they would have been willing to consider elevated LRT as well, again substantially reducing the $180m/mile figure. So in either case, it is invalid to compare PRT to the $200m/mile LRT cost in Seattle.

Last - stats for ridership in 2005 3Q reflect a total *decline* in ridership for autos, while transit ridership rose - so LRT was growing faster than all other traffic by a very large margin. In Q4, LRT ridership growth again outstripped all other modes. -- Transit Guest 19:22, 12 April 2006 (UTC)

"Such as basic costs per mile, and the fact that, for a given level of capacity, PRT systems will cost two to four times as much as LRT systems to construct and four to six times as much to extend into suburbs" -- this is complete utter nonsense. Go back and look at what I wrote above. PRT and LRT are at par in terms of costs per capacity. Depending on the design, PRT may be incrementally more expensive (i.e. 25-30%) not four times!

"And, of course, LRT *does* draw people away from cars." -- Light Rail Now is an advocacy site, and their numbers should not be trusted at face value any more than PRT advocacy sites are here. In fact, I think the LRT cost numbers should be removed until we verify that they are correct from a neutral source. A Transportation Enthusiast 04:25, 14 April 2006 (UTC)

"A recent survey of Metro Transit customers leaves no doubt that were it not for buses and light rail, many more people would be driving solo on the region's roads and highways. Three out of five train riders and two of five bus riders said they would've driven by themselves if transit were not available." More facts numbers available from Met Council Avidor 12:00, 14 April 2006 (UTC)

You ignored what I wrote: that traffic reduction within a congested corridor is the central reason such mass transit systems are considered, and that even before additional guideways are built to provide extra rush-hour capacity, PRT costs three times more because of the need to build guideways *both* directions and to build the crossing routes. Do the math yourself! Don't forget to add rights of way for stations and those other infrastructure facilities. FYI, DoT calculates that for all modes of transit, such facilities typically account for about 15% of capital costs, though since those are the only parts of the PRT system that require land, I'd expect their costs to be more than 15% of the total.

But now that the numbers are being calculated and made clear (i.e. that LRT is demonstrably cheaper), your answer is to say you think the numbers are cooked? Why are you suspicious of LRN's numbers? They provide cites to their data - do you have any evidence that it is incorrect or fabricated? The 2005 Q3 and Q4 is from official USDoT releases. The cost data are from published statistics from the transit agencies or DoT. They are far more reliable than, for example, SkyTran's "once we build the robot..." cost-per-mile estimates.

On a related note, I think that if we want to keep referring to SkyTran's anomalously cheap $0.8m per mile in the article, we need to mention the robot. It's why their costs are so low. -- Transit Guest 15:49, 14 April 2006 (UTC)

Transit Guest, go back and re-read the math I did earlier. The claim that PRT is four times as expensive as LRT has no basis in reality.

As for LRN's numbers, it's very easy to say something completely factual yet very misleading. I don't remember seeing Seattle's cost numbers in the LRN article about LRT costs, which leads me to believe they are selectively pulling favorable statistics and ignoring the unfavorable ones. Furthermore, the "Cyberspace Dream" article is so intentionally misleading, it leads me to distrust all content at that site. If they are willing to stoop to the level of bashing PRT with basic physics errors and displaying misleading images of an exaggerated Raytheon guideway in Minnesota (which never even considered Raytheon), what other facts would they twist in the name of pushing their favored technology? A Transportation Enthusiast 05:33, 24 April 2006 (UTC)

For reference, Taxi2000/SkywebExpress's estimate of US$70M for 12.8 miles for the SkyLoop Cincinnati system included all infrastructure, SkyLoop financials (archive.org). SkywebExpress' estimates have always included infrastructure costs as part of the per-mile cost. I believe ULTra has also, but don't have a reference handy. -- Ken MacLeod 11:58, 22 April 2006

Skyloop is dead... Skyweb Express (Taxi 2000) is nearly so. click on the "News" button on their websites....nothing. Avidor 18:09, 22 April 2006 (UTC)

PRT vs LRT in New Zealand - Deleted=

NOT archived. Check the history for "Deleted PRT vs LRT in New Zealand". Deleted because the content had no pertinance to this article and was, again, just basically a list of quotes from other websites. Fresheneesz 03:01, 13 April 2006 (UTC)

Watch Olson's PRT Amendment Get Voted Down in Minnesota

This just in...I just heard that Olson tried to attach an amendment to the Northstar bill for PRT...voted down 26-107.Avidor 17:20, 12 April 2006 (UTC)

Here's the video--Watch Mark Olson propose his PRT amendment. Watch the debate and watch it get voted down- This is the real world application of PRT- a nuisance amendment... a stalking horse to attack LRT and commuter rail. This article should reflect that reality...a reality you can see with your own eyes.Avidor 11:43, 20 April 2006 (UTC)

Separate this talk page into two: page discussion, and PRT discussion

Misplaced Pages isn't normally for discussing topics in general, more for improving the articles. But in this case, people (including myself) have been sucked into discussing the benefits or non-benefits of PRT - and this makes the talk page loooong. I'm proposing separating this page into the normal talk and a "discuss PRT" section. What does everyone think? Fresheneesz 02:50, 13 April 2006 (UTC)

Sure, but shouldn't you just call "discuss PRT" Avidor's Sandbox? That being the case, what would the benefit be to the main article? -13apr06 1:42 CDT

The benefit to the main article would be indirect, and because of benefit to the main talk page. My point in suggesting this is that random discussion can be put *there* rather than *here* - so we can improve the article without getting muddled by random stuff. Would you rather Avidor's sandbox be here, or somewhere else? Fresheneesz 05:42, 15 April 2006 (UTC)

The question is whether Avidor would use his sandbox. He wants his random stuff to have an impact on the writing of the main article. Since it would be easier for the rest of his to ignore the sandbox, why would he stop writing on this page (unless you strictly enforced it by Deletion)? And, from what I've been able to locate via Google, it appears that 90-95% of what Avidor has written here is repetitive of what he has already written somewhere else, so the horse has already left the barn. -15apr06 1:18 CDT

Well, I'd enforce deletion then. The problem is that I can't simply delete things on this page unless its clearly junk. But if we directed all non-article related ramblings elsewhere, then such things could be simply moved there, or deleted if users knowingly disobey the difference between article discussion and opinion discussion. Fresheneesz 23:04, 15 April 2006 (UTC)

Would the sandbox have a content standard? Because I wouldn't want to give thumbs up if we just end up creating another place on the Web where Avidor is free to make whatever claims he wants about PRT and PRT supporters. -15apr06 9:08p CDT

Sure, why not have a content standard. What do you propose? However, if we do make "just end up creating another place on the Web where Avidor is free to make whatever claims", it would be completely fine with me. I'm trying to improve the article PRT, and the talk page helps me do that - but since theres so much extraneous stuff on this page, its hard to do. Putting all that extraneous stuff somewhere else - and enforcing it - would make improving the article easier. Fresheneesz 04:08, 17 April 2006 (UTC)

On second thought, we should keep just this Talk page and enforce Deletion. No sandbox needs to be set up either, since Avidor already has a number of places to post his commentary. He links to them all the time. -16apr06 11:24p CDT

Would you be alright with me creating such a "sandbox" anyway? When I do, I would clean this talk page - archiving old stuff, and moving crap-content over to the "sandbox". We can still enforce deletion on this page (being nice about it to newcommers of course). Fresheneesz 18:42, 17 April 2006 (UTC)

Hey, I'll try anything once. Go ahead, what's the worst that could happen? -17apr06 4:28p CDT

K, its there. I've moved two topics there - noones used it by themselves yet. I just plan on moving the junk there till people get it. Fresheneesz 02:26, 22 April 2006 (UTC)

Skytran - former proposal?

Why does the note under Skytran read "former"? I'd definately be interested in a source for that. Whered you get that info from avidor? Fresheneesz 03:10, 13 April 2006 (UTC)

Avidor thinks the concept is defunct because of Malewicki's statement that he isn't actively working on it. But that doesn't explain why this "defunct" concept has adopted the name Unimodal and acquired strategic partners. "Dormant" might be more accurate than "former." -13apr06 1:00 CDT

Having taken a few minutes to look in Archive.org, I have found that Malewicki's "no such animal" statement was posted on Skytran.net as early as 2000. Given that (1) Skytran.net currently contains a "2004 Brochure" and (2) mentions the year 2006 on the home page, "no such animal" probably needs to be seen as a historical statement. Skytran shouldn't be characterized as "former" without more current evidence. -13apr06 1:25 CDT

This confirms my suspicions. Note that I will take Avidors edit in that case as an act of vandalism. Fresheneesz 05:51, 15 April 2006 (UTC)

Avidor complaining again

What gives Fresheneez a right to delete information that makes him uncomfortable?Avidor 11:26, 13 April 2006 (UTC)

No information you could put on here would make me uncomfortable. I deleted stuff that has NO bearing on this article. And place your comments under a related header, not in any header you want. I already wrote why I deleted two (so far) of your random ramblings. I will definately not delete anything you write if I can see that it *somehow* connects to the *writing* of this article. Note that you also have the "right" to put your comments back, but I assume that you value your time much more than I do, so pick your battles wisely. Fresheneesz 05:47, 15 April 2006 (UTC)

Actually, I have very little to complain about these days...read thisAvidor 17:06, 16 April 2006 (UTC)

Congratulations, it was unclear what the "amendment" was trying to get amended to. I looked up something on dean zimmerman, and the claim of bribery looks pretty thin. Fresheneesz 04:16, 17 April 2006 (UTC)

The Skytran-CETA Connection (deleted comment)

Deleted - no archive. Look under "The Skytran-CETA Connection (deleted comment)" in the history. This is the 3rd act of Avidor's talk page vandalism. Avidor: please stop - i'm not the only one requesting this.

More Real world skepticism of Skytran

moved this to the discussion page noted at the top of this talk page. Fresheneesz 10:06, 18 April 2006 (UTC)

Discussion of Robot Construction of Skytran

Moved to discussion page

What is meant by "political"?

"'PRT's problems are not technological, but political.'"

When I give examples of the real-world use of PRT to monkey-wrench transit funding such as the unsuccessful attempt by Rep. Mark Olson last week to attach a PRT amedment to HF2959, the Omnibus Capital Investment bill , proponents here call that irrelevant... yet, they cite some vague "political" reason for why PRT gets rejected in city after city, Wellington and Portland being the latest.

I think this needs to be explained in the article...what are the politics of PRT?Avidor 22:27, 21 April 2006 (UTC)

WHO cited political reasons for Wellington and Portland?

Political for PRT includes perceptions of bureaucratic or other decisionmaking inertia. One example is evaluating PRT as low capacity because each vehicle is small, which ignores aggregate capacity. Political can also refer to conflict with competing interest groups. Try researching PRT in Cardiff; resistance from bus advocates, while not the entire story, was still a large factor.

I don't understand your problem with Olson et al exercising their constitutional roles as elected officials in a pluralistic legislative process--the same pluralism that allows you to criticize. And the amendment failed--so, for you the process worked. What's the problem?

Or perhaps you could tell us Avidor, what you say the politics of PRT are? As if we couldn't guess. -21apr06, 6:44p CDT

I agree with Avidor, that sentence is misleading and is basically someone's opinion. PRT's problem is that it doesn't exist yet, for political and technological reasons. Trains are easy to build - because we've had the blue-prints for 200 years. PRT is still in the making, and thus its pretty much 100% that theres some technological problems. Fresheneesz 02:21, 22 April 2006 (UTC)

Wait... it doesn't say that anywhere in the article.. What gives? What are you talking about Avidor? Fresheneesz 02:23, 22 April 2006 (UTC)

Damnit, I misunderstood. In any case, Avidor you could write the politics yourself. Either on the real page, or you can put up a prototype here. Fresheneesz 02:45, 22 April 2006 (UTC)

"...political interference in the design requirements;"-- Please explain the meaning of "political interference" in that sentence (from the introduction) Can you prove that politicians interferred in the design process of PRT? Who, what, where, when? Please be specific.Avidor 13:50, 22 April 2006 (UTC)

"Not technological, but political" - fully functioning systems have been designed and built. CVS in Japan was killed by regulatory conflicts (according to LDemery's report) that had more to do with regulators' fears about recent rail accidents than any real safety issue. Cabintaxi was fully tested and ready to go until funding for the first installation fell through - a political decision. The sub-second headways debate is not about safety, but politics. I've yet to see a good technical argument against sub-second headways; most detractors say it will never be approved (by a political body), not that it isn't safe. A Transportation Enthusiast 13:44, 22 April 2006 (UTC)

Engineers are not politicians. Engineers sometimes advise politiciansAvidor 13:54, 22 April 2006 (UTC)

That's parsing. You don't have to be a politician to be political, any group of people can use power, influence and authority. A regulatory board, even if comprised by engineers, is clearly capable of making decisions politically as well as on technical grounds. And have you not heard of corporate politics? An example, which I have given before, was Raytheon corporate politics which forced the PRT2000 program to use pipe for the guideway that was too big, simply because it was made by another Raytheon division. -22apr06, 11:52a CDT

"political interference" - this means that someone took it upon themselves to deter people from supporting PRT. Plain and simple. It looks like you spend your life *doing* just that - so theres no question that theres "political interference". Fresheneesz 20:13, 22 April 2006 (UTC)

"political interference" - how many times are we going to rehash this? There is at least on indisputable case of political interference impacting a design: when the Nixon administration rushed the Morgantown PRT to completion before the 1972 (?) election, which resulted in several design compromises (mainly, that it became more GRT than PRT). There may be other examples, but that's the main one. A Transportation Enthusiast 05:04, 24 April 2006 (UTC)

Avidor already has written a section on the politics. It contained the phrase "PRT is a stalking horse" and was dropped from the main article because it is just his opinion. I believe that deleted section was also where he attributed to PRT proponents the quote "people don't like to ride with strangers"--which he was unable to prove any PRT group ever said or wrote. In other words, "what are the politics of PRT?" is just another attempt to revert the article to we say/they say. -24apr06, 1:42p CDT

Are Taxi 2000-Type Box-Frame Guideways More Expensive to Bend and Shape than Rails?

Trolley (tram) rails can be bent by hand... I've heard there are machines that bend rails also. An engineer told me that bending box frames with a slot at the top like the Taxi 2000 design would be very difficulet and expensive to shape.. that perhaps explains why Raytheon used pipes instead of box-frames. Another consideration may have been the need to bank the guideway on curves. Ever notice that the PRT graphics and animations dont show a banked PRT guideway on a curve?Avidor 18:52, 22 April 2006 (UTC)

The same bending techniques are used on the Taxi 2000 guideway. The pipes are smaller (because the box doesn't "ride" on the pipes) and the box frame is built as a truss connecting the machine-shaped pipes. Easements and banking are based on modern techniques pioneered by European high-speed railroads. These techniques take into account the vehicle's center of gravity (as it affects vehicle and guideway maintenance) and the passenger's sense of gravity (as it affects ride comfort). -- Ken MacLeod 20:28, 23 April 2006

Sounds like Ken (MacLeod) is saying the pieces are shaped before being assembled into a curved section. Did your engineer know this? I believe there is a page or two about it in Skyloop's rebuttal to OKI. See also the Guideway section of vectusprt.com and look at how the support tube allows banking. 24apr06, 12:34p CDT

Ken MacLeod: The gist of the "A Better Way to Design Railroad Transition Spirals" abstract is interesting, could you be so kind as to explain its main points in simpler language? What are the implications for PRT design? -24apr06, 12:46p CDT

It was and still is common to transition from a level, straight track or roadway to a banked, curved track based on a math formula that was simply a percentage of change of level and curve from where the straight track left off and the main part of the curve started (easement diagram). The simple formula doesn't take into account the forces on the vehicle, passengers, or against the track from the vehicle, particularly at higher speeds or smaller curves. The main points of the article are that 1) there are better formulas for the forces throughout the whole transistion, and 2) the formula should be applied to the "path" that is the vehicle's center of gravity as it goes through the curve and that the track should built to "make that happen". For high speed rail this means a smoother ride and less wear on the tracks and bogies/trucks. For lower speed PRT it means having normal ride comfort while maintaining speed through city corners. -- Ken MacLeod 15:37, 30 April 2006

Given such "new better formulas," how much would you guess curves in a 30-35mph PRT (vehicle size like Skyweb, ULTra, Vectus) have to be banked? Less than one might think? -01may06, 1:15p CDT

Picture from LRN - undue weight

The picture from light rail now places undue weight on that article. Its not appropriate, and the only reason I haven't removed it is because there is obviously differing opinions on whether it should be kept or not. PLEASE discuss it here, consensus *will* determine whether it stays or goes. Comments anyone? Fresheneesz 02:28, 22 April 2006 (UTC)

My compromise worked for nearly a week ;-) I'm happy with the image as long as it is captioned informatively as a simulated image by opponents. Its relative small size compared to the main image and positioning further down the page next to the Skepticism section reduce its weight. Stephen B Streater 08:25, 22 April 2006 (UTC)

I was content with your compromise, but apparently JzG disagreed. There's no question it's a misrepresentation intended to smear PRT: Avidor admitted that he created it as part of the PRT campaign in Minnesota, and Minnesota was considering Taxi2000, not Raytheon. Beyond that, the proportions appear to be exaggerated. Also, I have a problem with including a direct reference to the LRN article, which is basically a light rail marketing brochure. A Transportation Enthusiast 13:37, 22 April 2006 (UTC)

TE pretty much sums up the issues. It was created by a critic; the proportions are wrong; it is not the Taxi 2000 design proposed for Minneapolis; it is incomplete--the guideway framing would have been covered by a shell in a finished system; it links to an interest group that stands to gain from rejection of PRT; it links to an analysis that is demonstrably flawed by inaccurate understanding of PRT concepts. -22apr06, 12:03p CDT

The main argument (and only argument as far as i can tell) that this pic should be kept up is that it provides an opposing "view" - however, by putting in pictures like that, we are basically putting "words in PRT's mouth" - meaning that PRT isn't meant to look like that. Its simply an inaccurate picture, a picture of a situation that PRT would never be built like.

My point is that, while the other side of the argument should be given, pictures like that are simply propoganda and don't actually provide any meaningful argument. That is not to say that promotional PRT pictures *aren't* propoganda - however those pictures provide meaningful information about how PRT is designed to look, while the LRN picture doesn't have that sort of information. Fresheneesz 20:10, 22 April 2006 (UTC)

The proponents get their wacky picture and the critics get theirs... seems fair to me. Or maybe no pictures at all? I'd go for that. Avidor 20:22, 22 April 2006 (UTC)

Or we could remove both and include pictures of some of the real-world prototypes. I'd much prefer that to artists' renderings. Just zis Guy you know? 20:59, 22 April 2006 (UTC)

I agree, real-world pictures are much better. I emailed like 3 companies asking for pics - but i've got nothing. You're free to try too. Or we can simply take a picture and claim fair use (which I think would be appropriate in this case). Fresheneesz 22:23, 22 April 2006 (UTC)

I agree with real pictures too. We could have no pictures, but I prefer these two as most readers will have no idea what PRT is about. The exaggerated picture is still considerably smaller than a twelve lane highway or the Hammersmith flyover, which is what people are used to. Stephen B Streater 07:34, 23 April 2006 (UTC)

Regardless of whether it looks good or bad, it should still be identified as a misrepresentation. A Transportation Enthusiast 03:35, 24 April 2006 (UTC)

revert by JzG

JzG, you reverted my edit of the caption under the LRN picture. Why? I think it should be made clear that both SkyTran's picture and LRN's picture are suporimpositions onto real photographs. What is wrong with doing that? Fresheneesz 10:03, 23 April 2006 (UTC)

Capacity utilization and cost

I have removed the line from the cost section that indicates that PRT capacity utilization numbers would have to be proven in a real system. There is no disputing the capacity utilization of PRT, because it is inherent to the design. Let me explain:

PRT vehicles only move in response to demand, and simulations have shown that about one third of vehicles must be moving empty to keep up with demand. The only questionable piece of this is the 1/3 empty movement, since it is based on simulation. Therefore, I'm going to throw that 1/3 number out and analyze the system analytically, to determine the lower bound on capacity utlization (load factor).

Assume every station has a number of vehicles ready to take passengers. Also assume that every trip is a round trip: vehicle takes passengers to destination, then returns to its origin station. This is a worst case assumption since there are likely efficiencies to be gained by vehicles carrying passengers on the return trip, but I am just interested in the lower bound, and the the worst case is a full round trip: full one way, empty on the return.

Now, vehicles only run if they have at least one passenger. So this implies that the worst case load for any vehicle is 0.5 passengers - one for the forward trip, zero for the return. In other words, you can't average less than 0.5 persons per PRT vehicle, by design.

If we insert the maximum capacity per vehicle, we can easily calculate the lower bound for PRT load factor:

• 4-person vehicles: 0.5/4 = 12.5%
• 3-person vehicles: 0.5/3 = 16.6%
• 2-person vehicles: 0.5/2 = 25.0%

Keep in mind, this is a theoretical lower bound for capacity utilization, given PRT's design parameters. In practice, higher utilizations would be common, as (a) there will be more than 1 person per vehicle - I think a realistic assumption would be 1.2-1.5 per vehicle, and (b) simulations have shown that 1/3 empty vehicle movement is sufficient. Given 1.2 persons/vehicle and 1/3 empty vehicles (2/3 of vehicles are carrying passengers), the PRT load factors are:

• 4-person vehicles: (1.2 * 2/3)/4 = 20.0%
• 3-person vehicles: (1.2 * 2/3)/3 = 26.7%
• 2-person vehicles: (1.2 * 2/3)/2 = 40.0%

All of this, by the way, assumes full 24-hour on-demand service. No other public transit system except taxis can approach this level of utilization in a full 24-hour service mode.

Based on this, I've removed the line in the costs section that says PRT capacity utilization numbers would have to be proven. A Transportation Enthusiast 03:16, 24 April 2006 (UTC)

I don't remember much about Probability from when I took Statistics, but-- doesn't the 2/3 odds also apply to "return trips" not being empty? Just asking. -24apr06, 1:24p CDT

Not sure what you're asking here. The 2/3 number applies to all moving vehicles on the guideway. In other words, simulations have shown that if a total of X vehicles are moving, X/3 vehicles will be moving empty. Therefore, it's easy to incorporate that 1/3 empty factor into the capacity utilization calculation, because you just multiply the per-vehicle-in-use utilization by 2/3 (the percentage of vehicles full). I believe this 1/3 empty number is reliable, since it is based on extensive simulations, but I also listed the 1/2 empty number in the analysis above, for the simple reason that the "round trip" model is very easy to analyze analytically without requiring simulation results. A Transportation Enthusiast 18:41, 24 April 2006 (UTC)

Sorry, I wrote that before I figured out everything you were trying to accomplish. You are right-on so long as the load factor is the average for all vehicles that happen to be moving at any particular time, or period of time. I can think of a certain sequence of events at periods of extremely low demand that could lead to particular vehicles making a series of empty trips, but it would be such a small factor as to have no significant effect on the system-wide load factor. -24apr06, 2:23p CDT

The problem is that this assumes adequate number of vehicles, journey diversity, headways etc. It is speculative until proven. Everythign about PRT as a means of urban transit is; there are no systems in use on which to base anything but speculation. Just zis Guy you know? 22:50, 24 April 2006 (UTC)

But PRT is defined by its design. All this analysis assumes is the typical PRT design, in which vehicles only move in response to demand. There is no speculation about it. Go back up and read my analysis again. How would headway or journey diversity have an effect on the round trip model? A vehicle takes a passenger to its destination, then returns to its starting point. This is a very simple model that requires no assumptions about journey diversity or headways. You could have a PRT system with 7-minute headways and capacity utilization would be exactly what I stated above (though the system would be quite impractical). The only assumption is that the design would have at least one vehicle per station, which is a quite reasonable assumption. But even without that assumption, even with one single vehicle in the entire system, capacity utilization numbers would be similar, since vehicles only move in response to demand in every PRT system design I have ever seen. Do you dispute specific aspects of my arguments above? A Transportation Enthusiast 23:14, 24 April 2006 (UTC)

Assuming a car can nbe built which will do 500mph and return 200mpg, it will be possible to travel the length of the US in a couple of hours for a fraction of the cost of flying. A calculation based on assumptions for a theoretical system is inherently speculative. The problem here is that at least some of the "inherent" features appear to have been compromised or removed in the limited trial systems out there, so it's problematic to state that these will necessarily apply to all systems. Not only that, the prototypes bear little relation in scope and reach to the concept as discussed in the article. It's important not to multiply speculation. Just zis Guy you know? 12:15, 25 April 2006 (UTC)

JzG, please reread my analysis. It refers only to capacity utilization and makes no assumptions about speed, system capacity, or headway distance. The only assumption it makes is that vehicles move in response to demand, and that vehicle sizes are 2-4. This is inherent to every PRT design. It's not PRT if vehicles are larger, and it's not PRT if vehicles run on a schedule rather than on demand. There is no speculation here. Morgantown "PRT" is not true PRT for precisely the reason that its vehicles are too large and its service is more scheduled than on-demand. On-demand service and small vehicles define PRT, there is no speculation about it. A Transportation Enthusiast 12:40, 25 April 2006 (UTC)

OK, we're getting into That Area in which the line between concept and speculation gets blurred. The aspects of PRT that are speculation are any specific predictions of operational performance. What is not speculative are the basic principles of the PRT concept, where those principles are reasonable and consistent when considered individually and as a group. For instance, take capacity. The concept is that a large fleet of small vehicles, responding on-demand, make nonstop trips between stations; this speed combined with vehicle re-use achieves high capacity. That is the concept, skeptics should not be able to respond, "you can't say that, it's speculative." However, skeptics are welcome to make observations about factors that would affect actual capacity of a PRT in operation.

My point is that this article is currently not so much about PRT, as it is about what two opposing groups of people say PRT is. The skeptics need to allow proponents to define PRT's characteristics, so that can be discussed. Until now, proponents are defending PRT as they understand it, while opponents are attacking PRT as they understand it. The sides are not really arguing about the same thing. Stop the madness. -25apr06, 12:07 CDT

That would be nice. Except that PRT proponents here want to have it both ways. They claim all the benefits of the pure theoretical vision of full-scale city-wide PRT: hundreds of small, cheap, walkable stations; thin single-direction guideways; on-demand service to any location in town; non-stop operations; high speeds (25mph? 45mph? 65,ph); sub-second headways; seamless automated operations and control. But when asked about costs and implementation, they point to scaled down demonstration projects, speculative projections, or meaningless statistics. Which is it? Informed discussion gets really difficult when one side keeps shifting around to avoid specifics and trade-offs.

There also seems to be an excess of invalid comparisons to other transit modes, all in an effort to avoid dealing with the actual limitations of PRT. As an example, look at this discussion of capacity utilization: if it's all demand based, capacity utilization is irrelevant because so much of the system will lie idle. So what if PRT is using 20% of the current capacity if only 1% of the vehicles are in operation! Far more important to planners and taxpayers are maximum peak load in a heavily congeseted traffic corridor, total costs to construct, costs per passenger-mile, and the assumptions that underlie those numbers. -- Transit Guest 18:59, 27 April 2006 (UTC)

Oh come on, Transit Guest. Let's stop playing propaganda games here. The costs section (which was largely written by you) is properly speculative. You scoff at high density stations, thin guideways, on-demand service, non-stop operation, automated control, and sub-second headways, but you offer no proof whatsoever (either directly or indirectly) that any of this is impossible or even infeasible. The crux of your argument seems to be "this can't possibly work", which is basically just an opinion.

You write: "if it's all demand based, capacity utilization is irrelevant because so much of the system will lie idle" -- irrelevant? Is not capacity utilization an important factor in determining operational costs per passenger mile? Sure, high end capacity is an important characteristic of a transit system, but so is maintaining a decent level of capacity utilzation to reduce operational overhead. If not, then buses and trains would run every 6 minutes 24x7, right?

As for the capacity argument: PRT can achieve grade-separated LRT capacities with a single bidirectional (meaning one each way) guideway running at 0.5 second headways. Do you have a technical argument why 0.5 second headways are impossible? The regulatory argument is well known, and documented in the article. But what about a technical argument? There is plenty of evidence that very short headways are possible and feasible with current technology(plenty of theory, plus the AHS prototype at Berkeley) and I've not seen a shred of credible evidence to counter it. If your argument against short headways is purely regulatory, then that is a political concern and does not imply anything about the technical limitations of PRT capacity; regulations may change in response to new systems.

If you know of a solid technical argument against sub-second headways, then I would love to see it, because I've searched high and low and I can't find it. A Transportation Enthusiast 20:26, 27 April 2006 (UTC)

Your comment of 18:59 is exactly the mindset I was referring to. You cite the details of the concept accurately (small stations, flexible speed, nonstop, etc) but treat those as if they are by definition infeasible. In other words, you need to be able to stipulate the basic features of PRT so that this discussion can have a common basis for discussion.

"So what if PRT is using 20% of the current capacity if only 1% of the vehicles are in operation!" This tips the extent of the Skeptic misconception. PRT is demand-based. If at a particular time of day the demand is only 1% of capacity, then only 1% of the fleet needs to be moving (plus the empty 33% of the 1% that would be repositioned). A PRT vehicle being NOT "in operation" does not mean sitting in a barn, requiring some special procedure for it to go into service (unless it is out for maintenance). A vehicle sitting in a station, waiting for a passenger to show up, is not in operation. A person buys a ride and gets in, and it is now in operation. The same goes for vehicles on a storage siding (which can be in a barnlike building--this is the envisioned concept); the first vehicle in line can be instantly activated if needed, then the next, then the next.

The PRT concept is inherently flexible. If you are surprised that it can adapt to skeptics' doubts, you need to say how that flexibility is incompatible with the concept, rather than dismissively commenting "Informed discussion gets really difficult when one side keeps shifting around to avoid specifics and trade-offs." -28apr06, 11:52a CDT

Another Revert by JzG

JzG, I removed the full quote by Vuchic and replaced it with a summary, you reverted the change with no comment or mention on this talk page. Please tell me why that quote needs to be there when a concise summary with a citation is more than sufficient. You are the one who has actively promoted the idea of conciseness, and yet you revert this change here. Why? A Transportation Enthusiast 00:33, 25 April 2006 (UTC)

Because it makes a valid point. Just zis Guy you know? 12:20, 25 April 2006 (UTC)

And my version made the same point in a single line, with a citation so anyone can go and look at the full quote. Why conciceness everywhere and verbosity here? A Transportation Enthusiast 12:34, 25 April 2006 (UTC)

Proposal to remove this paragraph

The "Ridership Attraction section contains the following paragraph:

"Against this, the relationship of delays to traffic density for road travel is observed to be non-linear and the congestion delays which give rise to the predicted attraction may be eroded. London's Congestion Charge achieved approximately 20% reduction in private motor traffic, with an immediate and measurable improvement in journey times for all road transport in the City. This was achieved without substantial up-front investment, although revenue raised has been re-invested in additional public transport capacity."

This argument applies to any public transit mode, not just PRT. When auto congestion goes down, autos become less unattractive, thereby reducing the relative attractiveness of any public transit option. This same paragraph could appear verbatim in the light rail article, or any other public transit article. Perhaps this paragraph should be moved to the Public transport article since it is not specific to any particular mode? In any event, I don't think it belongs here because it's not specific to PRT.

It does, however, impact the supposed ridership attraction. I would rather that was not in there at all, since it has no verifiable basis in reality. Just zis Guy you know? 12:22, 25 April 2006 (UTC)

A ridership simulation is an analysis tool used by many transit professionals, not just PRT proponents. It's not 100% accurate (no analysis tool is 100% accurate) but it is still considered a useful tool for analyzing the relative ridership of different transit modes based on some basic assumptions about human behavior. To say that simulations "have no verifiable basis in reality" is wrong. Ridership studies do have some correlation with reality, otherwise nobody in the transit industry would bother with them. What about weather forecasting? Does the weather report have "no verifiable basis in reality"? Does the fact that weather forecasting is an inexact science make it completely irrelevant for the purposes of planning your day? A Transportation Enthusiast 13:56, 25 April 2006 (UTC)

Detailed explanations of my changes

JzG, once again you have reverted several of my changes without so much as a word here or in the edit comment. I took very special care to document all of my changes either in the edit comments or on this page, and you have reverted several of my changes en-masse with no explanation. I'm going to revert the changes back because I believe they have merit, and discuss each change here, line by line. Please, discuss here so we can come to consensus:

• Capacity vs Capacity Utilization - When reading the section on "capacity utilization", I realized that this discussion was not at all about capacity utilization, but just plain capacity. These are completely different terms. Capacity refers to how many people can be moved per hour, whereas capacity utilization is a measure of how much of the total capacity is being used. This section is not at all about utilization, but about capacity. I renamed it, you reverted it. It should be "capacity".

Not a problem. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

• Capacity vs Travel Speed - After further analysis of this section, I realized that the discussion of travel speed was out of place. Travel speed has a relatively small impact on capacity in transit systems, since capacity is mainly about the number of people that vehicles carry and the number of vehicles that are in operation, not how fast those vehicles move. Therefore, I moved the paragraph about speed of travel into its own section, and I expanded upon it a little bit to clarify the difference between average and max travel speed for the two types of systems (PRT vs line haul). I think this version is much more clearly presented: capacity arguments are more to the point without the largely irrelevant paragraph on travel speed.

You wrote: In theory, if peak speeds are similar, PRT should be faster on average than trains and buses, due to point-to-point, non-stop travel. And in theory if wishes were horses, beggars would ride. Since none of the test implementations and neither of the proposed installations in process has peak speds anywhere close to rail, this is irrelevant. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

OK, your edit is quite reasonable, and I rather like it better than mine, because it conveys the point without implying that peak speeds would be similar. This is exactly what I was trying to convey. Thank you. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

Thanks. And that, actually, is what I'm trying to get to every time: a suitably neutral form of words on which all can agree. Just zis Guy you know? 15:16, 26 April 2006 (UTC)

And I am confident we are now moving in that direction. A Transportation Enthusiast 16:15, 26 April 2006 (UTC)

• Capacity at low headways - I added the following line to the capacity section: PRT vehicles could theoretically achieve over 10,000 passengers per hour if half second headways were permitted. This statement is absolutely true and very well qualified ("could theoretically", "if... permitted"). At least one system that I know of (Taxi 2000) has been engineered for low headway operation even though the intended early applications were for 2-second headways. Low headways are controversial, true, and that is well reflected multiple times in the article, but this does not mean they are technologically impossible or even infeasible. The main argument against low headways is regulatory, and regulations change.

Theoretically if cars could travel at 500mph and return 200mpg it would be posisble to drive the length of the USA quicker and cheaper than flying. Since none of the systems in prototype or proposed installation demonstrates this feature, it is irrelevant. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

The fundamental difference here is that cars can't travel at 500mph (wind resistance would forbid it) and can't get 200mpg. But complete PRT systems have been engineered for 0.5 second headways, and there has been a prototype vehicle system (though not PRT) that actually operated at less than 0.5 second headways. This is not a pipe dream. The technology for half-second headways been demonstrated in a real world prototype (the automated highway systems at Berkeley back in the late 1990s) and has been engineered into at least one proposed system (Taxi 2000). The only thing lacking is real world testing of these systems at low headways. Surely you see the difference between this and 500mph autos, don't you?

Therefore, I believe the line about theoretical capacity at short headways should go back in, properly qualified that short headways may not be permitted by regulators. I don't buy your argument that the reader can calculate it him/herself, since the relationship between headway and capacity is not immediately evident to the casual reader. But adding the line with qualification allows the reader to decide for him/herself. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

Oh, right, so the test UniModal systems all travel at high speeds dot hey? Oh, wait, I forgot - there are none. Still, the data from the city-wide PRT systems surely support this data. Oh, wait, there are none of those either. Keep it real, ATE. We must not make dogmatic statements about what a system that actually does not yet exist can do. Just zis Guy you know? 09:44, 26 April 2006 (UTC)

"Dogmatic assertions?" Come on, JzG. The line I added was "PRT vehicles could theoretically achieve over 10,000 passengers per hour if half second headways were permitted." This is what you consider dogmatic? Just because you are skeptical of short headway designs (this is still about system designs, remember?) doesn't mean that these designs don't exist. The bottom line is: systems have been designed for low-headway operation. This is both true and verifiable. They haven't been tested or approved by regulatory agencies, though similar systems (AHS) have been tested at extremely low headway (around 0.25 seconds for AHS, I believe). This is both true and verifiable. The only thing lacking is regulatory approval and real world experience, which is why the statement I added was qualified with "theoretically" and "if...permitted". What exactly is wrong with adding this to the article?

Why don't we stop playing games and come to a compromise on this point like we have with some of the other points. I added what I thought was a reasonable presentation of sub-second headway capacity, which should be mentioned because it is a very important aspect of the PRT debate, and because it is true and verifiable. You removed it with no replacement. If you don't like the way I worded it, then reword it yourself in a way that is more to your liking, but please don't just remove the point altogether. A Transportation Enthusiast 13:56, 26 April 2006 (UTC)

• Ridership attraction - I changed the following: "simulations by advocates speculate that PRT might attract between 35% and 60% of automobile users" to " simulations indicate that PRT might attract between 25% and 60% of automobile users". There are two separate changes here:

1. "simulations speculate" to "simulations indicate" - a simulation is an engineering tool, and by nature cannot "speculate". Humans can speculate, humans can use simulation results to speculate, but simulations cannot speculate. This is a usage error. I changed it to "simulations indicate" because "might" properly qualifies the speculative nature of simulation versus real world data. Maybe "simulation results imply" would be better, but "simulations speculate" is wrong here.
2. removed "by proponents" - the OKI report was not written by proponents. The engineers contracted by OKI did their own ridership analysis with conservative assumptions (2-minute and 6-minute waits) and came to the same conclusion as proponent - that PRT ridership would approach 30%. This is an independent analysis by a neutral party. Therefore, there is no need to qualify this statement with "by proponents".

You are taking guesses piled on hypotheses and imbuing them with more credibility than they are worth. These simulations are really very tenuous - every time significant mode-switching has been predicted in the past, to my knowledge, it has failed to materialise because alhtough people say they would use this or that more envirnomentally friendly alternative, when it comes down to it they love their cars. So the statement, based on one simulation as far as you have stated thus far I think, is pie in the sky. I cannot express too strongly how uncomfortable I am with this particular claim. In my view it is incredibly unlikely ever to be delivered by any real system, and to assign numbers is really not warranted by the confidence one can place in the research. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

No, I'm not giving them any credibility. I'm just reporting what's there. I've never stated that simulations are superior to real world data, but they are still useful, especially in the comparative sense (if you are comparing two systems using the same ridership simulation, then the comparative analysis would tend to cancel out some of the inherent flaws of the assumptions).

But this is now a moot point, since I have no problem with your most recent edit, which presents the point in a properly speculative way. I still do have a problem with the paragraph following, since the discussion on the complexities of ridership analysis is not specific to just PRT analysis, but all transit analyses. See the separate section above for that discussion. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

I do not disagree that all ridership forecasts are to a degree speculative. But with light rail, for example, we have plenty of real-world installations to inform the speculation and correct any invalid assumptions. With PRT we have no such experience. So a ridership forecast for PRT is going to be less reliable than one for a light rail or other conventional scheme. I'm glad you accept the revised wording. The problem is always finding exactly the right form of words :-) Just zis Guy you know? 15:07, 26 April 2006 (UTC)

Yes, I think this issue is closed, although I still don't think the next paragraph fits. The congestion charge point is not specific to PRT, but applies to any form of public transit. I may try to revise this in the next few days to make this point more concise. A Transportation Enthusiast 16:25, 26 April 2006 (UTC)

• Cost and capacity utilization - I had written "Low operating costs also depend the relatively high capacity utilization inherent to PRT designs", and you changed it to "Low operating costs also depend on relatively high capacity utilization.". I've gone to great lengths explaining my rationale for this line above on this talk page, in the section "Capacity utilization and cost". The capacity utilization of PRT is inherent to its design. In other words, the very design that makes a transit system PRT (on demand service, small vehicles) puts an absolute mathematical lower bound on capacity utilization. If you change the system by making vehicles larger or implementing scheduled service it is no longer PRT. On demand service defines PRT, and the capacity utilization calculations above depend only on on demand service.

Inherent in a way that has been abandoned by at least one system on trial, so not actually inherent as such. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

I assume you are referring to Morgantown...? In that case, the system in which on demand service was abandoned is no longer PRT. It's well documented that there are no production PRT systems in existence, precisely because the changes to Morgantown made it GRT, not PRT. The fact remains that PRT is defined by on demand service; on demand service is inherent to PRT. And capacity utilization can be derived wholly based on this on demand service characteristic.

For these reasons, I still believe "inherent to PRT" is fully supportable and verifiable, and I would like to add it back in because it is an important point that isn't fully covered by your latest edit. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

You also added in your edit comment that 1 in 4 seats occupied is not a very good utilization number. On the contrary, it is quite high relative to other transit modes, especially given that it holds even for 24-hour travel. Buses and trains typically hover in the 10-25% range, but that is only because transit planners restrict capacity at low demand times to reduce costs. If trains and buses ran full round-the-clock service every day of the year as PRT proposes to do, then their capacity utilizations would drop through the floor -- likely less than 2-3%. PRT capacity utilization, on the other hand, is independent of demand. This is why the "relatively high" assertion is accurate. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

Nope. This is all still pie-in-the-sky stuff. You can't claim something is "inherent" when at least one of the supposed test systems abandoned it. That expresses far more confidence than can be justified by real-world experience. So what if, in abandoning this "inherent" feature you assert that it is no longer PRT? All that indicates is that the system doesn't work as advertised, causing at least one operator to compromise it. Remember, this is still a 4,000 word article on an unproven technology - we need to be very careful not to give the impression that it is real, because at present it is not. Just zis Guy you know? 09:41, 26 April 2006 (UTC)

With all due respect, JzG, your continued assertion that this is "pie in the sky" is patently absurd. You keep referring to Morgantown... why don't you look at true PRT systems that have been fully developed? German Cabintaxi is a fully developed, tested, and approved system. British ULTra has funding and regulatory approval and is working on its first implementation. Japanese CVS was ready to go before it was killed by paranoid regulators stung by a rash of rail accidents (according to LDemery's report). Korean-based Vectus is building a test track in Sweden. In the US, Taxi 2000 was fully engineered and had a functioning track/vehicle prototype. There is active development of PRT literally all over the world, with several systems well beyond the "do you think this will work?" phase, and you continue to refer to it as "pie in the sky". Maybe you still have SkyTran stuck in your head, which truly is an immature proposal. But using this term to refer to PRT in general is ridiculous.

Back to the point: only Morgantown abandoned small vehicles, and Morgantown is not PRT! Ask Avidor or Transit Guest, they will tell you the same thing: Morgantown is GRT, not PRT. You are citing as evidence the one example of a system that was compromised by bad design and rushed implementation. Bottom line: Morgantown was envisioned as PRT, and ended up not being PRT because they abandoned on-demand service. Is there any more clear evidence that on demand service is inherent to PRT designs? A Transportation Enthusiast 13:42, 26 April 2006 (UTC)

Look at it this way: you state that it is inherent in a PRT system; Morgantown was a PRT system; it abandoned this "inherent" property; you then say that it is no longer PRT. Which may be right - but who is to say that other systems would not go the same way? With such a very small sample base to work from we can't express excessive confidence. I am sure it is possible to express the concept without using the problematic word "inherent". Just zis Guy you know? 15:07, 26 April 2006 (UTC)

"but who is to say that other systems would not go the same way?" - but this is a discussion about PRT design, not failed PRT implementations -- that topic is covered elsewhere. The design of PRT does not allow for anything but on demand service. In any event, I can accept your most recent edit, which properly indicates that the relatively high capacity utilization is not just speculation, but rather a direct result of the on-demand service design. A Transportation Enthusiast 16:13, 26 April 2006 (UTC)

I am going to revert these changes back, because I believe they all have merit. If anyone has a problem with any of these changes, please discuss here under the above bulleted items. A Transportation Enthusiast 13:40, 25 April 2006 (UTC)

Ignoring ther fact that I already expressed my problems with them above. Ah well. Just zis Guy you know? 15:39, 25 April 2006 (UTC)

No, you never discussed these reverts at all. Your earlier comments on capacity utilization missed the point of my original discussion on the matter, that's why I reverted it. But in any event, most of your recent edits sound fine to me, with the exceptions noted above in the bulleted, threaded discussions. A Transportation Enthusiast 16:35, 25 April 2006 (UTC)

Please do not confuse not accepting your point wiht nmissing it. Just zis Guy you know? 09:41, 26 April 2006 (UTC)

Then perhaps you should better explain why you don't accept it, because by your response it appeared you missed my point. A Transportation Enthusiast 14:16, 26 April 2006 (UTC)

Different matter entirely. Just zis Guy you know? 15:07, 26 April 2006 (UTC)

Since we now seem to be working well together on these issues, I'm not worried about past misunderstandings. :-) A Transportation Enthusiast 16:19, 26 April 2006 (UTC)

Image from LRN

After writing this explanation of why the image from LRN should have a different caption, I will edit that caption into the page. Please discuss objections here. I would like to replace its current caption with this one:

"A photograph of a Raytheon PRT design superimposed on a photograph of a real street created by PRT opponents from Light Rail Now."

In this way, it is less of a blatant advertisement, and more of an objective explanatory caption. I *still* think that picture is inappropriate for this article, but that needs separate discussion. The caption as it stands does not point out the fact that the picture is not real, and is not what PRT systems are supposed to look like. The SkyTran picture labels it as superimposed (an edit I also made), and so should this picture. Fresheneesz 09:19, 25 April 2006 (UTC)

As stated above, that is not sufficiently neutral. It's an artist's impression by opponents, just as the skytran pic is an artist's impression by supporters. Just zis Guy you know? 12:21, 25 April 2006 (UTC)

It is a misrepresentation. Avidor knows the difference between Raytheon and Taxi 2000, yet he created this image with Raytheon guideway even though Taxi 2000 was the system under consideration. This is not just a simple case of an artist's impression. This is a superimposition of photographs, and the photograph used for the guideway is for a different guideway than was under consideration. A Transportation Enthusiast 12:32, 25 April 2006 (UTC)

The caption in the picture gives undue weight to LRN's article. Half the freaking caption is the name of the article and the organization. Its simple advertisement. It is fully neutral to say that it is a picture superimposed on another - how is it not neutral. I'm not trying to bash the picture, but it does need clarification - just as the SkyTran picture needed clarification.

Why haven't you reverted my edit to the caption under the SkyTran picture? - it is the exact same issue. Fresheneesz 21:13, 25 April 2006 (UTC)

If you refuse to discuss this JzG, then I'm going to reimpliment my edit. Fresheneesz 19:05, 29 April 2006 (UTC)

If you're going to revert, I'd wait at least a week for a reply. Even better, wait for someone else to do it (or not). After all, if your argument is that good, others will agree with you when the dust has settled a little. Stephen B Streater 21:53, 29 April 2006 (UTC)

Looks like JzG didn't log on between 19:05 and 19:06. Stephen B Streater 21:56, 29 April 2006 (UTC)

Ha, i'm sure. But he's the only person arguing his side. Whats your opinion on which caption should be done, or perhaps a compromise? Fresheneesz 22:21, 29 April 2006 (UTC)

Misplaced Pages is not a competition, but a cooperative venture with only one side - the consenus side. My view is that we should have the picture, but that the caption is too long and detailed. I'd rather have the description in the main text with a short caption. Personally, I'm happy with "artists impression", but could suggest something like: "A PRT simulation by detractors". All the links, explanation etc could go in the main text. The point is, as a reader, I'll skim the photos, and if I'm interested, I'll read the text. I've just looked at the link and PRT use the word simulation too. I'll show you what I mean... Stephen B Streater 08:59, 30 April 2006 (UTC)

It should be easy to access information in the previous caption, as it is now the first link in the section the picture is in. If I see the picture, this will be the first link I'll be interested in too. Also, the picture and section are more balanced in length, so the picture looks more like it is in the detractors' section. Stephen B Streater 09:08, 30 April 2006 (UTC)

It looks like a good edit to me. Thanks. Fresheneesz 11:02, 30 April 2006 (UTC)

Thanks :-) I've added a reference using the new reference technology so people won't have any difficulty finding it. Stephen B Streater 20:01, 30 April 2006 (UTC)

Now improved reference (using fab new ref technology) to avoid repetition and risk of repeated line being deleted). Now on to Unimodal discussion... Stephen B Streater 09:27, 1 May 2006 (UTC)

ULTra pictures

Hey, I got personal approval from Martin Lowson to have pictures of ULTra on wikipedia:

"Thanks for your enquiry. Nice to hear from you, although could you explain what your relation to the Misplaced Pages site is? In any case you are welcome to use any of the pictures on our website. I also attach a power point with some construction photos in it.

Thanks for your interest Martin"

Fresheneesz 22:21, 29 April 2006 (UTC)

Much better. We should aim to remove the two simulations and source an additional picture of Cabinentaxi. 62.73.137.190 12:45, 2 May 2006 (UTC)

I would think it'd be best if we had sort of a photomontage of a bunch of main PRT proposals. The review of this page mentions that it probably needs more pictures. Having a variety of pictures would give the reader a better idea of the range of things PRT can be. Fresheneesz 09:25, 4 May 2006 (UTC)

Capacity at Sub-second headways

A few weeks ago, I inserted the following line to the capacity section, which JzG reverted:

"PRT vehicles could theoretically achieve over 10,000 passengers per hour if half second headways were permitted."

After JzG reverted, we had a discussion above that never really came to an agreement. Currently, the line does not exist in the article. I believe that the point must be made that (a) sub-second headways are theoretically possible, and systems have been engineered for it, (b) an automated vehicle system running at sub-second headways was designed, prototyped, and tested successfully, and (c) PRT systems could move more than 10,000 passengers per hour per line with 0.5 second headways.

In point (b) above, I'm referring to the automated highway system prototype using Buick LeSabres, in which vehicles ran on a track at 60mph, separated by only 6 feet. The technology for sub-second headways (in this case, even less than 0.5 second headways) is here today. The main reason why PRT systems have not been proposed for sub-second headway operation is the current regulatory (i.e. political) environment is hostile to very short headways. This is documented in the article. But the point is, there is significant evidence that sub-second headways are both practical and safe, and very little evidence that they aren't. There's no reason why we shouldn't include the fact that, if a system were permitted by regulators to run at low headways, it could achieve capacities similar to grade-separated light rail lines. Of course, it should be properly qualified, but to not include it at all gives the impression that low-headway operation is impossible, which it certainly is not.

I'd like to discuss how to add this point to the capacity section in an NPOV way. I believe that my line above was neutral, but JzG disagreed, so I'd like to come to agreement here so this point can be properly represented in the article. A Transportation Enthusiast 16:05, 8 May 2006 (UTC)

No response to this yet, so I'm proposing the following addition to the capacity section:

"Capacity is inversely proportional to headway distance, so higher capacitites are possible if regulatory agencies allow shorter headways or vehicle platooning. Some PRT designs have been engineered for headways of one second or less, and automated highway system (AHS) researchers have successfully demonstrated platooning of modified automobiles at headways less than half a second. At half second headways, PRT could theoretically achieve capacities greater than 10,000 passengers per hour, per guideway."

All of this is true and verifiable. I see no problem with including it. If nobody objects, I will add it in the next few days. If you do object, please propose an alternate text that will make this point. A Transportation Enthusiast 05:12, 11 May 2006 (UTC)

I would agree as long as its not a large part of the artile, and if you clearly state all the conditions which have to be met for capacity to be at or above 10'000 vehicals/hour (including whether you are considering bi-directional or uni-). Since that paragraph doesn't state conditions for the capacity, I vote not to add it yet.

Theoretically, a PRT system could achieve capacities greater than 400 million passengers/hr if the speeds are high enough - specifics are needed to give that statement meaning. Fresheneesz 10:22, 11 May 2006 (UTC)

Most of the conditions are already stated in the existing capacity section. The two primary factors determining capacity on a guideway are headway and persons-per-vehicle, and persons-per-vehicle is already assumed to be 1.5 by the previous paragraph. The only assumption about speed is that speed would be sufficient to maintain the headway distance. At 30mph (45fps), which is a reasonable assumption for guideway speed, half-second headway implies 22 feet between the fronts of vehicles. If vehicles are 10 feet long (another reasonable assumption) this gives 12 feet separation, more than one full car length. A Transportation Enthusiast 14:59, 11 May 2006 (UTC)

A couple of nits to pick. 30mph is 44fps, not 45. Headway is from the back bumper of the first car to the front bumper of the second car. So 0.5 sec gives 22 feet headway, and (22 feet headway + 10 foot vehicle) gives 1.375 vehicles per second, 4950 vehicles per hour, and 7425 people / hour. pstudier 22:18, 11 May 2006 (UTC)

On further reading I have seen both usages of Headway and the article contradicts itself. The Free Dictionary says The distance in time or space that separates two vehicles traveling the same route. This means to me the distance from the rear of one vehicle to the front of the other. Wiktionary says (transportation jargon) interval of time or distance between two vehicles (e.g. buses) moving in the same direction, especially along the same pre-determined route. To me this could be interpreted either way. What is the "real" definition of Headway? pstudier 01:13, 12 May 2006 (UTC)

In all discussions of PRT headway, the headway has been defined as nose-to-nose. I think the confusion is caused by the fact that in most traditional cases, it doesn't matter. When you're dealing with trains running at 6-minute headways, the difference from tail-to-nose and nose-to-nose is negligible. But for PRT it is significant because the headways are so short that the length of the vehicle is significant. For PRT, I believe most (maybe all) PRT discussions assume headway is nose-to-nose, so I think my numbers are correct.

As for 44fps vs 45 fps, notice that I rounded down to 22 feet anyways, so the result was the same. :-) A Transportation Enthusiast 01:54, 12 May 2006 (UTC)

OK, I will accept nose-to-nose, because the example calculations in this article and elsewhere use this definition in the calculations. I have clarified the article to use this definition. So, at 0.5 seconds headway and 1.5 people per vehicle, we get 10,800 people/hour, and zero headways are impossible by definition. pstudier 02:42, 12 May 2006 (UTC)

On the other hand, 400M passengers/hr would imply 75,000 vehicles per second. Assuming 20 feet between the fronts of vehicles, this would require a speed of something like 1 million miles per hour, so no, 400M passengers/hr would not even be theoretically possible. I used the word "theoretical" basically as a qualifier because half second headway is controversial. There is nothing theoretical about the underlying assumptions (reasonable speed, reasonable passengers-per-vehicle, and half-second headway operation). A Transportation Enthusiast 14:59, 11 May 2006 (UTC)

My concern is that by asserting such a thing as "PRT could theoretically achieve capacities greater than 10,000 passengers per hour, per guideway.", I think you'll leave readers wondering what PRT *you* are talking about.

"an average of 1.5 persons per vehicle" is the only specific given under the capacity header. This leaves the following variables unknown:

• #1 your definition of headway (it only makes sense to calculate nose to tail, any other way doesn't make sense)
• length of one guideway ("per guideway")
• speed of the PRT you're assessing
• number of passangers per vehical (capacity doesn't mean "average")
• length of trip

Its 100% meaningless to say PRT can have capacities of XX passangers/hr/guideway. Capcity should be measured in passnger-miles per hour per mile of guideway. Not only that, PRT is a range of different designs. Saying something so general isn't something we should do.

For example, SkyTran traveling at .5 second headways at 100 mph, has a maximum capacity of 28'000 passanger-miles/hr/mile_of_guideway. 21'000 if assuming 1.5 passangers per vehical (which is an overestimate if you ask me).

I think it would be much better to give a *specific* example, like say "theoretically, at 1/2 second headways, UlTra (or SkyWeb, or something else) could get XXXX passenger miles per hour per mile of guideway. Fresheneesz 07:19, 12 May 2006 (UTC)

Re: 28,000 passanger-miles/hr/mile_of_guideway for SkyTran. Can you explain how you arrived at that number? A Transportation Enthusiast 11:27, 12 May 2006 (UTC)

Re: capacity units: I'm not familiar with the "passenger-miles/hr/mile_of_guideway" way of measuring capacity. Do you have any references for this? The rest of the section of capacity uses the more common definition of "passengers/hr". In other words, if you stand at a point on the line/guideway and count the number of passengers passing that point -- that's the definition of maximum capacity that is used here. A Transportation Enthusiast 12:55, 12 May 2006 (UTC)

Re: capacity vs max capacity: I agree, it's tough to compare trains and PRT in this way because they are so different. A 4-person PRT system running at 2-seconds headway has a theoretical maximum capacity of 4*1800 = 7200 passengers/hr, but unlike trains, passengers would not pack into PRT vehicles because they are all going different directions. So they use the average load factor to determine "maximum" PRT capacity, which is misleading because the average load factor can vary greatly. For example, the load factor might be 1.2 passengers/vehicle for the morning commute, but much higher (2.5 or more?) for a baseball game (where people generally go in groups of at least 2). So using 1.5 might be a high estimate for a commute, but a low estimate for a sporting event. Perhaps we should expand on this point in the article, because I think it underlines the difficulty in comparing PRT systems to trains and buses -- in many ways, you really are comparing apples to oranges. A Transportation Enthusiast 12:55, 12 May 2006 (UTC)

So just refresh my memory, which of the systems in widespread use has sub-second headways? Just zis Guy you know? 17:35, 12 May 2006 (UTC)

Have I somehow implied in this discussion that sub-second headways are "in widespread use"? A Transportation Enthusiast 19:58, 12 May 2006 (UTC)

As far as I recall there are precisely none (0) systems which have even trialled it. Just zis Guy you know? 10:42, 14 May 2006 (UTC)

(1) CVS was tested at 1-second. (2) I've read somewhere that Cabintaxi was tested at sub-second headways, but I've been unable to verify this. (3) The AHS platooning test demonstrated vehicles at quarter-second headways. (4) Sub-second headways were being pursued in the 1970s and Congress discussed funding an effort to develop the technology, but the effort was unsuccessful (allegedly due to political interference from rail advocates). (5) Most systems in development today are advertised to run at 2 seconds, but at least one (Taxi 2000, there may be others) was designed and engineered for much shorter headways, and people involved have indicated that regulators would be willing to consider shorter headways with increased operational experience.

Now, considering all this, doesn't the capacity at short headways merit even a qualified sentence in the article? A Transportation Enthusiast 13:25, 14 May 2006 (UTC)

I fail to see how JzG's comment in any way relates.

Well, I really just made up "passenger-miles/hr/mile_of_guideway", because its more useful than your version (which may or may not be the conventional way). My justification is, P-mi/hr/MoG (hehe) shows the relationship between guideway and capacity. Adding more "points" into a system doesn't make any logical sense, but multiplying miles of guideway by "my" measurement gives you the maximum capacity of the system - while your definition does not (because "your" measurement doesn't take into acount the pods on the track, only pods moving past a point).

"Re: 28,000 ... Can you explain how you arrived at that number?"

2 passangers/pod * 100 miles/hr * 1 pod/(72 feet) = 14'666 passanger-miles / hr / mile (of guideway). Mutiply that by two for both directions, and there you have it - 29'333 pa-mi / hr / mi (of guideway). I rounded when I first gave the figure. Of course, this is really "pod-miles/hr/mile times 2" because i'm not includeing the estimated 1/3 of vehicals that need be unmanned - in which case the figure would be almost 20'000. Fresheneesz 07:43, 14 May 2006 (UTC)

Sorry, small correction: .5 second headways for skytran is 73.3 feet. Fresheneesz 07:50, 14 May 2006 (UTC)

Slightly larger correction: any figure for Skytran is 100% hypothetical. All figures should be based on systems which have at least been prototyped. Just zis Guy you know? 10:43, 14 May 2006 (UTC)

JzG, I was addressing a specific question I was asked by ATE. Please quit being a dick - we're trying to have a civil dicussion here and you're just inserting irrellevant thoughts. I'm not advocating putting my calculations into the article. Fresheneesz 20:01, 14 May 2006 (UTC)

Oh also, my calculations weren't skytran specific. They are maximum capacity for ANY system that has an average of 200 seat miles/hour/vehical. SkyTran might be hypothetical, but it doesn't have to by SkyTran to easily match that capacity. Fresheneesz 20:07, 14 May 2006 (UTC)

Please don't forget WP:NPA. Personal attacks don't persuade people and insults don't work in cyberspace. You might also like to consider that not everyone has time to read everything that is typed here. Stephen B Streater 21:26, 14 May 2006 (UTC)

Is there a guideline against administrators smugly dancing on the grave of articles they kill with little justification?

About 100 articles get deleted every day. More would get deleted if people had more time. As soon as PRT happens, all PRT systems and related articles will gain credibility. In the mean time, PRT systems must gain credibility outside WP for the consensus to shift. Add more independent references to the sections as they come up to assist this. Stephen B Streater 06:42, 15 May 2006 (UTC)

I'm sure everyone can appreciate the frustration of seeing irrelevant and pompous ridicule of the serious discussion we're having, by a very well respected admin like JzG. I was not trying to insult, I was asking (rather rudely, and for the second time) that he contribute constructively. I wish I didn't have to ask. Fresheneesz 06:22, 15 May 2006 (UTC)

I concur 100% with Fresheneesz. I too have been frustrated by JzG's attitude in all of this. "Pompous ridicule" describes it perfectly. From the first day, I've been motivated to make this a truly neutral treatment of PRT, but JzG still treats me like a snake oil salesman. When I've made well-intentioned changes to the article, he's reverted them en masse, forcing me to explain every single change in excruciating detail here (most of which he later accepted, once he bothered to read what I wrote). He's repeatedly asked us to be civil and discuss changes rationally, but here, once again, he jumps into a reasonable discussion and poisons it with sarcastic, irrelevant one-liners.

Honestly it's soured me on the entire Misplaced Pages experience. This is the first article I've worked on, and it will likely be the last, because frankly I'm sick of defending myself and my edits. Why bother putting my time and energy into improving an article, when an arrogant admin with an itchy trigger finger is just going to swoop in and revert all my well-intentioned changes without even reading my edit comments? Apparently Skybum (a very good editor who had contributed much to this article) has grown tired of it too... he seems to have given up on Misplaced Pages entirely. I'm not far behind. If I want to deal with arrogant, condescending authorities, I can just as easily get pulled over for speeding on the Interstate. A Transportation Enthusiast 07:53, 15 May 2006 (UTC)

First time checking in here in a long while. You're quite correct, this entire experience was an exercise in frustration and absurdity for me. After JzG began doing blanket deletions of all of my edits, without any justification whatsoever, and refusing to respond to me on the talk page (except to occasionally threaten to ban me), I simply had to leave. His blatant bias and reckless edits and threats make him unfit to be an administrator. If I had the time, I would gladly go through the process of filing formal complaints against him. However, I don't. If somebody else wants to lead the charge, I'll happily chip in a bit.

Note that I'm not decrying the presence of an actually neutral administrator around here. This page has, in fact, at times been corrupted by pro-PRT propaganda. It's just that JzG, with his pre-existing favorable disposition towards Avidor, has frequently acted as though the best way to balance pro-PRT propaganda is to delete it and replace it with anti-PRT propaganda, rather than actually work together to create a strictly factual, neutral article. Skybum 19:55, 20 May 2006 (UTC)

Well, I think Avidor has gone MIA, and JZG has withdrawn a bit as well. I think it would be very safe to edit this page again, as long as we work to maintain a clear consensus. Stephen Streater has been very helpful in resolving many of the issues I had with JzG. Also, although I and you may think JzG has abused his power enough to warrent revoking it - many people don't think so, and he *is* a very well respected editor (although It seems hes only been editing for a year). Not only that, he makes good edits lots of the time - just not here. None of this should be a problem anymore, as long as we all realize that wikipedia works based on consensus, not logic (because whos to say whats logical and whats not - consensus). Fresheneesz 00:42, 21 May 2006 (UTC)

Re: Avidor going away: Avidor apparently doesn't feel the need to be here anymore, IMO for two reasons: (1) the recent (April) Minnesota election is over, and (2) JzG has assumed his watchdog role. In fact, JzG more or less told Avidor to leave so that he "can wrestle this thing to the ground" -- apparently that means locking down pages and doing mass reverts.

Re: JzG's actions: I continue to assume good faith on JzG's part, but at the very least, he has shown very bad judgement in this whole conflict. He came into this debate seeing two sides to an argument, and automatically assumed that both sides were equidistant from the "neutral" position. This, even in the face of much evidence that Avidor's views were extreme. So, he basically bisected our viewpoints and assumed the midpoint of our views was the neutral position. And then it got even worse than that, when we tried to contribute in a constructive way and he treated us like used car salesmen, automatically rejecting our edits without even reading our comments.

The most distressing thing is that JzG's own reputation makes him largely impervious to Misplaced Pages's formal corrective measures. Whenever we've sought external help, we've been rebuffed by other admins that just assume that JzG is infallible and must be correct. Of course, we don't have anywhere near the reputation nor edit history of JzG, so his word is almost automatically trusted over ours. So what recourse do we have? The best we can do is fight tooth and nail for every single good faith edit we try to make. Who has the time for all that?

Maybe I should write a new article here on Misplaced Pages: How to Forcibly Inject Your POV into Misplaced Pages, and describe the tactics that Avidor has so successfully employed: (1) antagonize reasonable editors until they lose their temper and strike back, (2) cry foul and claim that you've been attacked by said editors, (3) wait for a friendly admin to arrive who doesn't do his research and automatically assumes that both your views are equally valid, and finally, (4) sit back, relax, and watch as said administrator methodically and forcibly pushes the article POV in your direction.

It doesn't say much about the integrity of Misplaced Pages's process, does it? A Transportation Enthusiast 04:31, 21 May 2006 (UTC)

This is partly a problem with the niche nature of the PRT article. A subject with thousands or even ten editors would be immune from destructive behaviour by one politically motivated opponent. PRT is attracting a slow but steady stream of editors and over time the article will, through random motion, trend in the right direction, rather like Brownian motion. See my vote in Misplaced Pages:Articles_for_deletion/UniModal/proposed, which is incidentlly still open. If PRT has had such a hard time, how would the even more specialised Unimodal article fare against a concerted attack from a supporter of a rival system? Stephen B Streater 08:08, 21 May 2006 (UTC)

I do agree that one of the problems is that there are so few editors working on it. But I disagree that PRT is attracting new editors (other than you, Stephen). In fact, the level of hostility has driven away some people who might have been able to contribute usefully, most notably SkyBum. First it was Avidor and his attacks, then it was JzG and his mass reverts and threats. So rather than a healthy debate of the topic, of knowledgeable editors making WP:BOLD changes to the article, we have a few lingering editors who make every edit with great caution, lest they piss off an admin who's already decided that the article is exactly as it should be (even though his knowledge of PRT is limited). Not the Misplaced Pages way. A Transportation Enthusiast 06:13, 23 May 2006 (UTC)

I think the main problem is education. If wikipedians are educated on how to use wikipedia, then they'll know how to handle any weird situtation. But as it stands (a phrase I find myself using alot lately), most of us are poorly educated on the processes and policies of wikipedia, and thus are swamped out when opposed by people who *are* educated. Fresheneesz 10:54, 21 May 2006 (UTC)

But it goes beyond education. Sure, we've all misstepped, and JzG has interceded to correct us, sometimes firmly. I've learned a lot from JzG. But, unfortunately, he has gone beyond that, assuming that we have an agenda just because we happen to be adding verifiable information about PRT to the article. Sometimes I think that JzG really believes Avidor's "cult" claims, and treats supposed "proponents" as promoters of some kind pseudo-scientific fraud. Even when we add a verifiable claim, he rejects it for some other reason, i.e. "article balance", which is basically a crock; for something as grounded in verifiable scientific theory as PRT is, suppressing verifiable information in the name of one editor's sense of "balance" is indefensible. A Transportation Enthusiast 06:13, 23 May 2006 (UTC)

Well I don't think it matters much at the moment, since the article seems not to be very heavily edited at the moment. And if its a problem in the future, all we have to do is learn to draw a clear consensus, and even us low ranking wikipedians can overpower an admin. Fresheneesz 08:02, 23 May 2006 (UTC)

The way to build consensus is to get knowledgeable people involved in the debate. But people knowledgeable about PRT are labelled as "proponents" and their involvement is summarily rejected. So we've tried to get non-PRT people involved, but they don't know enough to contribute in a meaningful way, so they rely on a trusted source... and the source they trust is JzG! So this article has become a snapshot of the limited knowledge of a single editor, who admits that he didn't know anything about PRT until a few months ago. Personally I believe I am the perfect person to work on this page, since I have absolutely no attachment to PRT but I've done a ton of reading on the topic and I feel like I have a deep understanding of both sides of the debate. But because of my knowledge, I wear the scarlet "P" (proponent) so my input is automatically treated with hostility. Same with SkyBum and Fresheneesz. And so the article stagnates. A Transportation Enthusiast 14:18, 23 May 2006 (UTC)

The rules of WP are designed so that you don't have to be an expert to check an article. As an expert, you should know where to find reliable sources that anyone can verify. You are not allowed original research, which includes a home-made synthesis of uncited sources. This reduces the need for experts when it comes to checking the article. Stephen B Streater 14:34, 23 May 2006 (UTC)

There have been at least two occasions where I added verifiable information that was reverted by JzG. In one case, he rejected based on "article balance", another time he didn't even provide justification, even though I used very detailed edit comments to justify the changes (which were very incremental in nature). I had to basically beg JzG to consider each change with detailed explanations of every single change, here on the talk page, after which he conceded most of the points. But if he had read my edits and comments in the first place, we could have avoided the entire drawn-out debate. Instead, he reverted based solely on the assumption that I was editing with an agenda. I believe Fresheneesz and Skybum can relate similar instances of unexplained mass reverts of good faith edits. It gets exasperating after a while, constantly having an admin treating your edits with such disdain, and it's already driven at least one good editor away (Skybum).

So while the rules of WP should allow for anyone to edit an article, the rule for this article seems to be "anyone may edit, except for those individuals whom JzG perceives as proponents, which basically includes everyone with extensive knowledge of PRT even if they have no inherent bias (financial, political, or otherwise) ". This basically ensures that the article will reflect JzG's POV, which is that PRT is "Quixotic dream". A Transportation Enthusiast 15:21, 23 May 2006 (UTC)

Have a look at what JzG does and you'll that as an admin he is massively overworked and so he only looks in detail at things when people debate with him. You've said he conceded most of the points, which is good on a controversial subject. Anyway, he's had a recent bereavement so don't treat him too harshly. And the article doesn't look too bad. Unimodal will need a clean up though ;-) Stephen B Streater 16:07, 23 May 2006 (UTC)

Actually, I do understand that JzG is very busy here, and in fact I think that is a big reason for his lapse in judgement in this case (note, I'm not accusing him of bad faith, just bad judgement in his dealings on this page). My main beef is that, if he is going to participate, he should invest the time necessary to do it right. Reverts from a respected admin carry much more weight than reverts from ordinary users, and as such should be executed with great care. If JzG is too busy to invest in that level of care, then maybe he should defer to some other mediator.

And yes, I do respect that he is struggling with other issues right now. That's one of the reasons I haven't been editing the article directly in the last few days. When he is back, we can resume the debate. Please don't view my comments here as an attack on JzG personally. I have great respect for him as an editor and admin, and I've learned a great deal from him. But he's not infallible, and I believe several of his actions here have been incorrect. A Transportation Enthusiast 16:41, 23 May 2006 (UTC)

I'm sure he'll respect you all the more for not taking advantage of his absence. Discipline is the key to WP. And Patience. And finding a consensus. I'm sure it will all come right in the end. Stephen B Streater 17:17, 23 May 2006 (UTC)

In other words, thats all in the past. Quit complaining and lets just remember what we learned about wikipedias version of red tape : ) . Its much better than the redtape in the US government... Fresheneesz 02:25, 24 May 2006 (UTC)

"Its much better than the redtape in the US government..." - Well that says a lot! :-) A Transportation Enthusiast 04:08, 24 May 2006 (UTC)

headway

" the headway, the distance between the fronts of vehicles"

dictionary.com: "The clear vertical space beneath a ceiling or archway; clearance." "The distance in time or space that separates two vehicles traveling the same route."

Merriam-Webster: "the time interval between two vehicles traveling in the same direction on the same route

Google: vehicle headway definition

• Definitions of headways, gaps and several related terms -- Suggested clarifications for the Highway Capacity Manual 2000; headway defined as front-to-front.
• Transportation Research Board, 2004 Meeting Minutes, Committee on Traffic Flow Theory and Characteristics; section: Distinction between gaps and headways -- headway defined as front-to-front. "The traditional definition of a “headway” is the time interval between the front of a vehicle passing a point and the front of the next vehicle passing the same point." "The 2000 Highway Capacity Manual defines the term headway in Chapter 5 as “The time, in seconds, between two successive vehicles as they pass a point on the roadway, measured from the same common feature of both vehicles (for example, the front axle or the front bumper)”.

-- Ken MacLeod 07:50, 14 May 2006

The definition of headway is "clearance" or "space ahead", which is implied in the word itself. Headway is defined as the time or space that separates two vehicals - IE the air between them, NOT the space between their fronts. Its headway, not head-to-head way.

I would change that definition, but it seems people already trust the current one. It should be changed. Fresheneesz 07:28, 12 May 2006 (UTC)

I would support a change to show the space between the vehicles, not the distance between their fronts. Stephen B Streater 08:49, 12 May 2006 (UTC)

Whenever I've read about headway in PRT designs, headway is defined as nose-to-nose distance. It may have a different meaning outside of the context of PRT, but for PRT it seems to be defined as nose-to-nose. A Transportation Enthusiast 11:06, 12 May 2006 (UTC)

OK. I'm not an expert. It may be worth adding a reference to show this to discourage someone from changing it. Stephen B Streater 11:14, 12 May 2006 (UTC)

I've done some research on the definition of headway. It appears that, in the transit domain, headway is defined as service frequency. I derived this from reading several transit sources (mostly dealing with rail systems)... and here (PDF) is one that provides an actual definition (page 14). This seems to be the accepted definiton of headway, not the distance between vehicles, but rather the interval between vehicles -- i.e. the time that passes between two vehicles passing the same point. The difference is subtle but crucial: "distance between" implies the space from the rear of the front car to the front of its follower, but "interval between" implies the time it takes for vehicles to pass a given point -- which would generally be measured front-to-front (or perhaps rear-to-rear, but generally not rear-to-front).

Now, headway is generally quoted in units of seconds or minutes, which is counterintuitive for a frequency measure, so perhaps it's easier to think of transit headway as the inverse of service frequency; i.e. headway is more akin to wavelength if we were talking about waves instead of vehicles.

So it appears that the PRT definition of headway is in line with the general transit definition. As I mentioned earlier, I think the problem is that, traditionally, "headway" is used primarily in rail systems, where the difference between front-to-front and rear-to-front is negligible with respect to the long headways (minutes) involved. For that reason, the exact definition is not well defined in most places. A Transportation Enthusiast 12:17, 12 May 2006 (UTC)

The definitions in that PDF are either not consistant, or badly named. "Headway" is defined as *both* the time-interval and distance-interval between vehicals. The main point is that its between the vehicals, not between the fronts. The reason I say the names are not consistant is that service frequency seems to be the freqency of vehicals, which is different than the time-interval between vehicals (although they are in many cases approximately the same). In every single definition of headway, I've never seen, heard of, or thought of front to front measurements. Front to front just doesn't make sense. Fresheneesz 08:00, 14 May 2006 (UTC)

• - "In the context of PRT, "headway" means the nose-to-nose time spacing between two sequential vehicles."
• - "With traffic speeds averaging approximately 40 mph, a nose-to-nose headway of 3 s is equivalent to about 176 ft."
• - "At 30 mph, a more reasonable urban PRT speed, half-second headway corresponds to a nose-to-nose spacing of 22 feet."

Being my own devils advocate - it looks like many people use the nose-to-nose definition. I still think that definition is misleading, inconsistant, and not the familiar definition to normal readers. Note that one of the sources above is ridiculing PRT - using a quote that provides context for bashing (as is the usual way with prt opponents). The nose-to-nose headway is a ridiculous definition, and it is NOT accurate/useful to use when talking about safety and stopping distance - however it *is* useful for calculations of carrying capacity.

In short, I think we should use "headway" to mean the more general definition of "space/time ahead" the inerval beteween vehicals. If we want to talk about the frequency of vehicals, we should use the phrase "service frequency". Fresheneesz 08:12, 14 May 2006 (UTC)

I have always understood it as nose-to-nose spacing as well, but I believe that the people who discuss motor vehicle headways (which are more closely related) are not entirely consistent in this. Just zis Guy you know? 10:45, 14 May 2006 (UTC)

"Headway" is a basic number for describing systems. From that number, many characteristics of systems can be derived, described, and compared. For safety purposes, absolutely, vehicle length, speed, and stopping distances (normal and emergency) must be taken into account -- those factors are then described as a "minimum safe headway" (for a particular system). For example, the minimum safe headway on highways is different for cars and semi-trucks, and total lane vehicle capacity is measured differently based on the typical mix of vehicles. Passenger capacity is derived from vehicle capacity (based on headway, or the number of vehicles per hour per lane). For example, a typical free-flowing highway lane has a passenger car capacity of 2000-2400 vehicles per hour per lane. At 1.2 persons per vehicle, a passenger capacity of 2400-2880 pph. Ken MacLeod 08:40, 14 May 2006

Capacity, Revisited

OK, it seems the capacity discussion above has fizzled without a consensus, but there were several good points raised. Fresheneesz made a good point that the capacity calculations seem to be arbitrary, with no discussion as to how they are derived. Now that I've thought about this a few days, and re-read the section several times, I agree. This section needs improvement. I'd like to take a stab at it, with this basic outline:

1. Briefly describe how max capacity is typically derived for a transit system: i.e. max passengers per vehicle multiplied by maximum vehicles per hour (service frequency).
2. Mention the fact that PRT approaches capacity differently than other public transit modes: PRT is typically small vehicles with high service frequency, whereas buses and trains are large vehicles with lower service frequency.
3. Briefly discuss the headway issue, its controversy, and its effect on capacity. Mention that 2-second headways have received regulatory approval, 1-second headways have been tested but never approved, 0.5 second headways have been theorized and simulated, and lower headways have been demonstrated as part of AHS platooning research.
4. Discuss the point that, while the theoretical maximum capacity of 4-passenger PRT would be based on the full 4 passengers per vehicle (load factor), most analyses assume a smaller load factor due to the point-to-point nature of PRT. So while buses and trains may simply assume the maximum passengers-per-vehicle, PRT capacity predictions generally assume some number less than the theoretical maximum. This assumed PRT load factor may vary significantly for different scenarios. For the morning commute, it may be as low as 1.2, but for sporting events it may be 2.2 or larger.
5. Show a table of maximum PRT capacity for different assumptions: vehicle load factors of 1.2, 2.2, and 4; and headways of 2s, 1s, and 0.5s.

I'd like to take a stab at this in the next few days. Would anybody object if I made these changes right in the article itself? A Transportation Enthusiast 02:04, 18 May 2006 (UTC)

Most of that seems good to me. One thing, you should have a source in-line for "2-second headways have received regulatory approval". Otherwise it might become the object of dispute later. Same for "1-second headways have been tested". Also, a table might make the capacity section unnessesarily large. I would say that if you want to do a table, make it have something like 3 distinctly different capacity calcuations - to show the range of things that can be calculated. I wonder though, if that enters in upon NOR. Fresheneesz 00:49, 19 May 2006 (UTC)

Why I won't be coming back

First of all, I want to say that I am sorry for JzG's loss. Furthermore, whatever problems I may have with him, I recognize that he's put a lot of effort into improving Misplaced Pages, and the vast majority of that effort has been sincere and valuable. Even his contributions to the PRT article have been at least 50% helpful. Since he has erroneously pidgeonholed me as a rabid pro-PRT supporter, he'd probably be surprised at how often I agree with his POV: as a recent example, I agree with him that Unimodal is not deserving of its own page, at least until it acquires either significant funding or has built significant actual hardware.

Given that our perspectives aren't really that far apart, why am I now so frankly hostile toward him? Because his behavior here has been, frankly, inexcusably bombastic. One of the great things about Misplaced Pages's technology is that whatever one says is faithfully recorded, always. Therefore, however stupid an argument might get, it can never spiral into a "you said this / no I said that" dead-end fight. At least, that's what I thought, until JzG showed up.

I had made a series of completely factual and neutral edits, which Jzg then largely reverted, with a snide comment about "removing apparent advertorial". Not only did he assume bad faith on my part, but he re-introduced flat-out wrong information in the process. Now, here's the odd part: he explained his actions by citing a flat-out mis-reading of what I'd written (he read the word "re-invented" as "reviewed", completely changing the meaning of a sentence). If I had actually written what he thought I had written, then one sentence would have been "advertorial". But I didn't, and it wasn't, yet he erased nearly everything that I had written, and furthermore threatened to lock the article if I made such edits again.

I reverted his reverts, and posted a correction of his mistake, and explanation of my edits. He reverted my edits again, stating that "History indicates that disinterested third parties are more likely ot be neutral than proponents." Again, the assumption of bad faith. Even more perplexingly, he again insisted on mis-reading what I had written, and again threatened to lock the article! Even though he was entirely, wholly, provably, irrefutably and in every way in error!

I attempted to correct him, yet again, and he never replied. Okay, so I wasn't as polite as I could have been, so I tried again, giving him every benefit of the doubt. He never replied. Nor did he ever reply to me again, even when I tried to engage him.

This episode was just one of many frustrations that he visited upon this page. Between his mass reverts, assumptions of bad faith, bizarrely persistent mis-readings, threats to lock the page, and refusals to discuss anything with me, I had no choice but to conclude that working with JzG was an absolute impossibility. If he is acting in good faith, then he is simply rushing his edits to the point of incompetence; on the other hand, if he is acting competently, then he must also be acting in bad faith. Either way, given the vast disparity in power between him and I, there is no way that I can make a difference here. If he were to apologize and change his ways -- or lose his admin status -- I would certainly come back, but I doubt that will ever happen. And yes, this has shaken my faith in Misplaced Pages to the core. Skybum 22:35, 24 May 2006 (UTC)

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