Misplaced Pages

Revision as of 23:26, 24 March 2006

{{FAC}} should be substituted at the top of the article talk page

Gravities vs. m/s^2

I think gravities are more meaningful for an average person, and this is an encyclopedia. So, I plan to put the gravities as the primary unit, with m/s^2 in parenthesis.

misc

Reverted away from copyrighted text from www.lightrailnow.org/features/f_prt_2005-01.htm

Braking

P1

The reason that PRT guideways can sustain much higher traffic rate has absolutely nothing to do with stopping distance; in fact, their stopping distance is generally longer than an automobile's. Rather, it is their computer-controlled reaction time which is the critical factor. This is why the DMV recommends a 2-second separation between street vehicles (also known as the headway distance); not because a car traveling at 65 mph can stop in two seconds, but because that's the reaction time of the average driver. Once the driver reacts, they can apply the brakes and presumably match the deceleration rate of whatever is in front of them. Because PRT vehicles are computer-controlled, their reaction time is measured in milliseconds instead of seconds. This allows for much shorter headway distances, and much higher traffic flows.

The accellerations originally in the article would still be fatal for most people (except in the case of instantaneous accellerations lasting a few milliseconds at most, which is not pertinent to the current discussion). Moreover, braking does not effect route capacity in any substantial way -- reaction time is essentially the only important factor here. If ATRA has reviewed and approved this text, then I'm frankly dissapointed in them; these sort of physically-impossible claims are precisely the sort of thing which causes conventional-transit advocates to disparage PRT. There's an excellent paper discussing precisely this subject, which is linked from the Innovative Transportation Technologies website; I just need to go through the work of finding it and summarizing it. I'll try to have that done by sometime tomorrow. Skybum 18:49, 4 October 2005 (UTC)

Read the following PDF: Safe Design of Personal Rapid Transit Systems. On the subject of braking, and headway, it has this to say on pages 6 & 7, after first giving the somewhat complex equation for safe minimum headway distances (emphasis mine):

T_min = (L/V) + t_c + k(V/2)(1/a_e - 1/a_f)

The first term is the time required for a vehicle of length L travelling at a velocity V to travel one vehicle length. It is the minimum possible headway. The second term t_c is the time required to detect the malfunction and apply the brakes. The third term is proportional to the available stopping distance after the brakes are fully applied divided by the cruising speed V. a_e is the emergency braking rate and af is the failure braking rate. k is a dimensionless number included to increase safety.

To appreciate the fundamentals of the question of minimum headway, consider some numerical values. For the Taxi 2000 vehicle, L = 3 m and V = 48 kph. Therefore

L/V = 0.224 sec.

Consider t_c. It is the sum of the time interval between failure occurrence and braking initiation, and the time required to fully apply the brakes. In an automobile, the time to react to an emergency depends on human reaction time. Under automation, the time interval needed to detect the failure and to begin applying the brakes depends on the characteristics of the control system. In a PRT system designed for maximum throughput, it is necessary for the zone controller to be able to sense the position of each vehicle at any point, i. e., vehicle-position data must be continuously available. The first part of t_c is about 0.1 sec plus the much smaller time for the computer to react. The second part of t_c must be as short as practical with current technology. With electromagnetic braking, this time is the inductive time constant of the motor, which is of the order of 10 msec. For a state-of-the-art PRT system, I therefore estimate

t_c = 0.12 sec.

Consider the third term in equation (1). The term a_e must be as high as practical. If all passengers are seated, simple experiments show that a 0.5g deceleration will not throw a passenger out of the seat. If passengers are standing, even half this acceleration is too much, so one of the requirements of PRT safety is that the vehicle be designed for all passengers seated.

This passage makes it clear that the reaction time (t_c) is the dominant factor in the determination of headway distances. Moreover, it makes it clear that the emergency braking accleration (a_e), while desireable to be as possible, is acceptable around a level of 0.5g. These values can be found repeated throughout the web, such as here (emphasis mine):

The usual acceleration and deceleration of the vehicle is 1/4 g, or 8 feet/sec^2. In an emergency, the Taxi 2000 system would stop using 4/10 g, or 12.8 feet/sec^2. a system that would go 25 mph (37 feet per second) the safe following distance to avoid any possible collisions becomes (37 fps) / 2*(12.8 fpss) = 1.445 seconds, plus the .004 seconds of reaction time, for a total of 1.45 seconds.

Finally, my point about the harm that these kind of false claims (of PRT requiring, or benefiting from, high deceleration rates) can cause was not theoretical. Check out here, or here, which alas uses our PRT page as a source for its criticism.

I believe that this should be the final word on the topic. Unless anybody has some further arguments, I will be heavily revising this info on the main PRT page tomorrow. -- Skybum 04:42, 6 October 2005 (UTC)

Thank-you very much for the excellent work. User:Ray Van De Walker

P2

Why is braking distance so important? When one drives a car, one certainly can not stop in the distance between cars. What am I missing? pstudier 22:18, 2005 Apr 6 (UTC)

I at least, am a more cautious driver than the people in your area. Some of us might say we're willing to take the risk, but some people who say they are willing to take the risk might change their minds after they have an accident. So, in most places, safety laws require public transit vehicles to keep a full stopping distance between themselves and anything they could hit. This lowers the number of vehicles that can fit on the road or guideway or whatever. In turn, this reduces the rate at which the road or guideway can be depreciated. This in turn increases the fares or public costs substantially, because the roads or guideways are the most expensive part of a transport system. User:Ray Van De Walker

Excuse me, but breaking distance is DEFINITELY a factor because the faster a car can break, the closer they can be together. Why is this the case? It is because the law says it is the case. Public transportation vehicles are required to travel far enough behind the vehicle in front of them so that it could stop IN THAT DISTANCE. For example, if the vehicle in front of a public transportation vehicle stopped at infinite deceleration (immediately), the public vehicle would still be able to break in time. Thus, to comply with regulations, cars must be able to stop quickly enough - and the more cars that fit on the track, the larger the track capacity can be. This is a HUGE factor in this sort of thing. The normal road system is failing in large and midsized cities now because of lack of capacity. If PRT wants to solve that, capacity is going to be a main issue. Fresheneesz 00:20, 30 November 2005 (UTC)

Did you read my comments in the rest of this section? They decisively answer the braking question. You are correct that capacity is the main issue, but braking distance is absolutely not what determines capacity. To recap what I've said above, this is because the only thing you'll need to brake to avoid is the vehicle ahead of you, which will either be A.) Gradually braking, or B.) Coasting to a stop. Those are the only two possibilities. Therefore, all that a vehicle needs to do is 1.) Notice that it needs to brake (this is the critical factor: reaction time), then 2.) Match the rate of deceleration of the vehicle ahead of it. As you can hopefully see, the velocity at which you brake is not a factor, so long as it matches the velocity of whatever is in front of you.

Automobiles are different, because they have to deal with cross-traffic. This can create scenarios where there is essentially a "brick wall" in front of the vehicle, and the closer you can get to instantaneous deceleration, the better. PRT doesn't have to deal with this scenario, however. PRT is more akin to a freeway, where the recommend 2-second following distance is absolutely not determined by braking speed (at highway speeds, cars require 6-10 seconds to brake). 1-2 seconds is a typical human reaction time, allowing drivers to notice and match the deceleration of whatever is in front of them. This is essentially the same as PRT. However, in PRT, the reaction time is computer-based rather than human-awareness-based, and this -- and not braking -- is what allows for much closer following distances (as close as a few milliseconds under the most optimistic scenarios), and much greater route capacities. Skybum 07:59, 30 November 2005 (UTC)

Well... you *did* read all of what I wrote right? Because the issue is not saftey here, it is public transit *laws*. Of course, to avoid collision, a vehicle must only decelerate about as quickly as the vehicle in front of it. However, the law states otherwise - and *that* is the problem. But I do see what you're saying, however I think that both breaking time and reaction time are large factors. Another thing to consider is the semantics of the situation - personally I consider "breaking" to include reaction time in the case of PRT - because it is automatic, integral to breaking, and invariant. For example, in the Skytran system, the vehicles can decelerate in 1/2 second in an emergency, which I think you can agree contributes to the stopping distance slightly more than the decreased reaction time. Fresheneesz 08:39, 30 November 2005 (UTC)

No, the laws aren't the problem, because the laws for every transportation mode are different, and there are no laws that currently apply to PRT. Trains and busses, for example, can require as much as 30 seconds to come to a full stop when travelling at full speed (because anything much quicker than that would kill their unbelted passengers). They are still allowed to operate. Skybum 17:41, 30 November 2005 (UTC)

They are allowed to operate because they put enough distance between themselves and another train to stop in that distance. Do you think that PRT will be allowed to be built without regulation? Most likely, legislators will be the *same* or *more strict* requirements on safety issues, such as breaking distance, compared to trains, busses or other forms of transportation. There are no laws about PRT now, because it is a minuscule part of our society if anything. Fresheneesz 20:22, 30 November 2005 (UTC)

Yes, legislators will, and should, regulate PRT. It is in everybody's interest to make sure that PRT is as safe as possible. However, it is also important that people not equate safety (or headway distances) with braking speed, because on a closed-track off-grade system, they are almost unrelated. In fact, higher braking speeds can lead to decreases in safetey. Consider a city bus travelling at, say, 45mph. For the sake of its unbelted passengers, it cannot brake at any faster than 1/4g, which means a stopping time of about 8.5 seconds. If it stops much faster than this, passengers will be thrown from their seats and across the bus, severely injuring and possibly even killing them. Thus there is no safety advantage to having a bus stop any more quickly than this (and indeed, they can't do so). Yet busses are allowed to operate at 2-second following distances, because it is the reaction time of the driver which is the important factor. As long as the bus can reliably brake at 1/4g, it does not need to brake any faster.

This principle is universally recognized by transportation planners -- except for those coming from the rail industry. This is because its traffic models have to account for massive frieght trains that have a stopping distance of literally miles -- in other words, beyond the perception & reaction time of the train driver, and reliant upon the signaling system and the stopping distance of the train itself. Because of this, the following distance for trains is determined by its braking speed, and even this is somewhat archaic, given the advent or modern real-time signaling systems. No other land-based transportation system works this way, or should. I have no fear that PRT will be regulated like this, even if the assholes at LightRailNow can't grok the concept.

Anyhow, it is almost certain that PRT headways will be determined in the same fashion that car and bus headways are -- reaction-time-based rather than braking-distance-based. Because regulators are intrinsically conservative, they'll probably start with the same two-second rule that autos use, and gradually reduce this as the system proves itself to be safe and reliable. That's how PRT will achieve a high route capacity. Meanwhile, making claims about its supposedly superior braking velocities is in fact harmful to the PRT cause. This is because if PRT vehicles were to brake more quickly than other vehicles, they would soon begin throwing their occupants through the windshield, in the service of avoiding a collision. That's not an effective safety technique, and isn't in any case how PRT works, so there's no point in talking about it -- except perhaps to dispell the myths surrounding the subject.

By the way, I like the edits that you've been doing. Keep up the good work! Skybum 06:16, 1 December 2005 (UTC)

Thanks! And I agree, breaking speeds has little to do with safety on a basically isolated linear system like PRT systems are. And I hope you're right about future legislation. What does the lightrail now people have against PRT anyway - it's not like *they're* making any more money off light rail than anyone else. Anyone smart enough would put their money in a good PRT system rather than pushing it back down. But in any case, I think *this* discussion (I mean a very very consolidated version of it) should be put in the article - rather than skirting the subject entirely. Fresheneesz 06:25, 1 December 2005 (UTC)

I would love to see a condensed, accurate version of the braking facts in the article as well. User:Ray Van De Walker

WHOA !! : All the above appears to assume isolated, individual PRT vehicles. That will not be the case in any economically practical implementation. Anti-collision, guidance and individual join/leave-platoon will be autonomous-local in a platoon of many individual PRT vehicles, electronically coupled, in both position, speed, acceleration and function, with little or no gap between. The sole neighborhood-located control function will be local routing, average speed control and ON-GRADE crossing control. Central control will handle metro-wide traffic-routing and overall speed supervision. Forget central detailed control of individual vehicles or even of platoons. Your autonomous-chauffeur will be VERY skilled !

" little or no gap between" - perhaps eventually, but thats not a necessity of PRT, and shouldn't appear in the article. Not only that, PRT will most likely *not* be so implemented because of paranoid concerns of legislators and the idiot public. About central control, I agree. Fresheneesz 09:59, 27 December 2005 (UTC)

"The law": I don't think all countries where this page is available have the same laws. Pysa, 217.118.41.215 20:38, 15 February 2006 (UTC)

P3

People (Skybum!!!) we had a discussion of hard braking some time back. I just located one of the PRT designers I read about who wants to use 6G decelerations to overcome those train laws that grow headway. It's Doug Maliewicki, designer of skytran. See User:Ray Van De Walker

Maliewicki has designed race cars, right? So he likes an "exciting" ride. In terms of ride comfort, SkyTran looks to be way way out there on the edge of the PRT envelope. Ed Anderson's design appears to be in the safe & sane class, 0.25g max acceleration, 0.23g max jerk.

I think the breaking issue can be split up into three different scenarios:

1. Regular braking - normal operation. Typically 0.25g.
2. Emergency braking - fault operation, i.e. vehicle stall or some other minor event. Typically 0.4g.
3. Catastrophic braking - multiple simultaneous faults or an act of God has created a catastrophic scenario that requires extreme braking.

From what I've seen, good design and an elevated guideway ensures that (3) would be an extremely rare event (MTBF in the hundreds of years). However, it appears that Skytran is still accounting for it in their design. In other words, even if an incredible series of events causes a brick wall stop on the guideway, Skytran offers an extreme braking option coupled with automobile-type vehicle restraints that would preserve the passengers.

So, the point that Maliewicki seems to be making is: even thought the brick wall stop scenario is incredibly rare in PRT designs, we can still design for it by providing vehicle restraints and hard braking. It's almost as if he is addressing the regulatory problem (the brick-wall stop requirement that might currently apply to PRT) rather than the engineering problem.

But the problem with this argument is: it clouds the issue of safety because it implies that 60g braking would be required for safe everyday operation, which would certainly not be the case in a properly engineered system. Regular emergency braking would be more than sufficient for all non-catastrophic fault scenarios.

An economic question, then, would be whether the rarity of the 6g stop would warrant the cost and any weight penalty for including a 6g-capable braking system. If it could be performed by the normal braking system (a LIM, say), so much the better. It would be interesting to know if there was anything other than headway that helped ULTra get UK safety approval, and the Swedish regulatory criteria that Vectus will have to meet.

In addition, there's a question of a belting system for 6g. Would liability concerns allow self-belting by riders? Would mandatory passive-belting be preferred, an automatic system that would add moving parts? The latter might be easier in the cockpit-like SkyTran, while Taxi 2000, ULTra and Vectus might find it difficult. Again, extra expense for a rare event.

I'm guessing that Taxi2000 and others did this exact same analysis and came to this same conclusion. They seem to have decided to put their efforts into designing for the more common stop scenarios (and ensuring that brick wall stops never occur).

There is a point of diminishing returns when it comes to engineering for safety. Consider light rail: there is certainly a safety risk to having trains share the road with vehicles and pedestrians. But is it worth the cost (financial and otherwise) to build tunnels or elevated platforms everywhere? Generally no. It's an acceptable risk.

The same can be said of the PRT brick-wall stop -- designing systems to withstand such a rare scenario is overkill. Unfortunately, the regulatory situation hasn't caught up to the engineering reality, and that's why you have systems like Skytran trying solve phantom problems.

WVU PRT separate article?

WVU PRT should be seperate article? wikiveterans please advise Codeczero 16:29 Feb 21, 2003 (UTC)

Hi, welcome! As it is, WVU PRT fits well in this article: it is on-topic, and only when an article gets very long we need to split it. - Patrick 20:26 Feb 21, 2003 (UTC)

good info in here but it reads like someones PRO PRT lobbying piece still.. Triptych 02:57, 9 Jan 2004 (UTC)

Not anymore. There are quite a lot of disadvantages listed, and I just put in the guideway choice issue and the dual mode versus single mode debate. Now, the problem is to get the article organized a bit more. Too many of the points mentioned (as advantages or disadvantages or as specs) apply only to one type of guideway but not to another or to a single mode system but not a dual mode system, and this is not made clear.

I wrote the original article, and I'm still one of the biggest contributors (I often fail to log in). I started off pretty ignorant, and very neutral on the topic. I have experience with biomedical software and safety engineering. So I read up on the topic. Unfortunately, most of the people who write books about this thing, and really understand it are enthusiasts (of course). Most of the people who debunk it are clearly doing the capitalization and overhead math wrong. Some of the older advocates say this is happening on purpose to persuade the politicians to buy the wrong transit stuff. User:Ray Van De Walker 2004-01-27 09:20Z

I am always amazed at the naivete of alas too many PRT enthusiasts (and here I am not refering to those who have edited this article, for they seem a level headed lot) and sympathisers . No, PRT systems are not singled out specifically for destruction, yes they will get destroyed mercilessly if they are not nimble. The transit market is all too often a "dog eat dog" world of rather fierce competition between competing kinds of systems, competing companies within the same systems and local financial interests striving for attention. PRT projects get caught in the crossfire most of the time, or brushed aside with a slight shove because of their fragility. Entrenched transit technologies in traditional transport establishments can react in a very brutal way to menacing innovations, and this has happened to much stronger and well prepared projects than what PRT systems are offering. One example is the air cushion aerotrain developped by Jean Bertin in France. It went as far as full scale prototypes and a long test track several kilometers long. The development of the TGV, the Train Grande Vitesse (ultra high speed train) by France's national railways, the SNCF was an effort meant to crush the aerotrain, which it considered as a dangerous competitor. Hundeds of millions of Euros were spent in R and D by the SNCF, dwarfing the aerotrain research budget. Even greater sums were spent on the new dedicated infrastructure for the TGV. The SNCF was successful. Companies which sell trams, buses or commuter wagons cannot be expected to lie down and say . "OK you have the right stuff and we have the wrong stuff." They can be expected to try every trick in the book to wipe any PRT proposal off the map, as they wipe out other competitors in the traditional bus and tram domain. The only potential allies are car companies, which stand to gain as much by making myriads of PRT vehicles as they are making cars, if personal vehicles are allowed (in single mode as well as in dual modes personal vehicles are possible, though they are rarely discussed) but there is no reason for them to leave the status quo. One should note though that Ford research labs proposed a new PRT system called PRISM, in December 2003.

NO ALLIES - Auto manufacturers will NOT EVER be allies, because PRT vehicles will be like DC-3s -- good for over 50 years, at least the mechanical part.

Some sort of PRT planned in Finland

I can remember reading an article about some sort of a trial of a PRT system being planned in Finland. If I can remember right, it would (at first) be a line from Helsinki-Vantaa airport to some points in Helsinki (or well, they called it a high speed "driverless taxi" moving on a predesigned route, as far as I can remember, but isn't that a PRT system then..). Would anyone have any more info on this, as I couldn't find anything from Google? It would be an interesting addition to the article.--HJV 20:35, 27 August 2005 (UTC)

Portal-Portal Evolutionary PRT

A successful version of PRT will eventually 1) Offer PORTAL-PORTAL transportation (ABSOLUTELY ESSENTIAL), regardless of the distance without changing one's seat; 2) Require NO GUIDEWAYS whatever : Optical, computer and control technology are already sufficient to meet that challenge; 3) Evolve from systems serving only small areas from which manually-operated transportation (auto traffic) has been absolutely barred -- The user whose destination is within must park his auto and continue on PPPRT. The areas served by PPPRT will gradually expand until autos are universally no longer operable in urban areas; 4) In their final form, offer very high speed operation on longer trips ("Guidetube", Group-Mode, 500 MPH+).

What do you mean no guideways? A guideway is the support of the vehicle, it's the "road" on which the "car" travels. Explain your alternate definition of "guideway". And, what is the difference between normal PRT and PPPRT (portal to portal PRT) ? I thought normal PRT *was* portal to portal... Finally, what's the point of this explanation? Fresheneesz 03:42, 9 December 2005 (UTC)

I'm scratching my head on this one too. If there is supporting third-party material that can document... er, whatever the hypothesis is here, then that'd be great. Otherwise, I suspect that this would fall under the "Misplaced Pages is not the place for original research" policy, and leave it at that. Skybum 05:22, 9 December 2005 (UTC)

A "guideway" is any arrangement in which the steering function, normally provided by the operator of a conventional automotive vehicle, is instead provided by the path of travel, such as a rail, monorail or the like. Another variation is where the steering function is provided by magnetic , optical or other such features embedded in the surface of the "guideway". Thus, the device providing the guidance does not necessarily support the vertical or horizontal thrusts of the vehicle.

Please provide directions to information concerning a "normal PRT" which IS in fact operated "portal-to-portal" (door-to-door), without designated stops and without designated paths of travel (routes). 162.42.87.107 16:17, 16 December 2005 (UTC)

I did not write the above, but I do not find it confusing, either. The DARPA Grand Challenge has successfully developed autonomous vehicles. Make them cabs, summoned by cellphone, and we have portal-to-portal PRT without guideways or new infrastructure. It -is- research, but it's pretty obvious research. Also, no government investment is required. Some regulatory changes might be needed to permit robot drivers. User:Ray Van De Walker

PRT is a guided system by definition. Otherwise you're looking at an Automated highway system, which is a Dual mode transit system derived from current automobiles, Smart car, or Driverless car. Ken MacLeod 20:38, 2 February 2006 (UTC)

Really? Well, anyway, I think if we got driverless electric taxicabs, we'd have most of the utility of PRT. It wouldn't be quite as safe, I believe, because the taxis wouldn't be on a separated grade. It might also have higher maintenance and energy costs, but the gross functionality is very similar. User:Ray Van De Walker

Definition of PRT

I have always thought of Personal Rapid Transit as defined by its title. By its title, the definition should be: A mass transit system which employs small, on-demand vehicals that are able to transport riders anywhere on the system. This would mean that cars are a form of mass transit. Although most PRT systems are automated, I don't think thats a neccessary property of PRT. To this end, I might be generalizing a bit too much. But I do think it would be interesting to note that the car is VERY VERY simliar to PRT if not PRT itself. Fresheneesz 18:54, 10 March 2006 (UTC)

From a literal perspective, yes, cars are "personal rapit transit". But the term PRT has been associated with automated vehicles for over 30 years now, so I don't think there's any ambiguity there; cars are not PRT by the commonly accepted definition of the term. 72.65.19.184 22:37, 10 March 2006 (UTC)

Regulatory Concerns

I have removed the references to Michael D. Setty and myself for several reasons. First, our primary position has been substantially misrepresented. As we have stated repeatedly on www.publictransit.us: there are, at most, several dozen U.S. urban-suburban corridors with passenger traffic density sufficient to justify the investment required for "light rail" development. By contrast, there are at least several hundred urban corridors with sufficient traffic density to justify some level of investment for improved bus service. Second, we are not the only professional transit consultants who are not interested in PRT development; i.e. check the Institute of Transportation Engineers list of "transportation consultants" (http://www.ite.org/directories/consultants.asp) and count the number of firms advertising "PRT." Third, we have provided significant details regarding PRT safety standards, most recently from the California Public Utilities Commission and earlier research on the application of "uniform" safety standards for "trackguided" vehicles in Japan from the mid-1970s led to abandonment of major PRT plans in Tokyo. Yes we are PRT skeptics, but we are not the only ones with this POV.

Ldemery

Point 1: misrepresentation of your position:

How can your position be misrepresented when we quoted directly from your own website?

Point 2: few other professionals promote PRT:

There is a large distinction between not promoting PRT, and actively speaking out against the technology. You fall into the latter category, and therefore your views are fair game for critical analysis.

Point 3: details on your PRT skepticism:

If you have such details, then add them to the article so that they may be shared by all. I searched your web site and the Internet, but found no detail on your PRT position other than the references I posted in the article.

Honestly, I don't see how any of this text can be suppressed. It's 100% factual and backed by links to your own site. If you have links that better define your position, then please provide them, otherwise I am going to put the text back in. A Transportation Enthusiast

----

I checked out the references you listed (California Public Utilities Commission letter and the report on AGT in Japan). I still see no PRT safety analysis by you or Setty. In both cases, the analysis is of regulations that would currently apply to PRT by virtue of being rail bound vehicles. Two points:

1. These represent local regulations for the state of California and the country of Japan. Therefore, the only argument made in these references is that PRT would not be certified under current regulatory law in these two places. It says nothing about whether it would be certified safe in other states/countries, or even whether the California/Japan regulations might change in the future to reflect advancements in technology.
2. As far as I know, you and Mr. Setty have never publicly responded to the claims of PRT safety with a technical rebuttal. For example, the "Cyber Dreams" paper was written anonymously by a light rail advocate, and has been disputed by at least three separate rebuttals, but you cite the original article with no comment on the rebuttals.

You and Mr. Setty have every right to be skeptical of PRT. However, when you take such a strong stand against a technology without presenting any technical justification, then people are going to challenge your conclusions. That's exactly what PRT advocates have done. The article text reflected this accurately and factually. I see no problem with including that text back in. A Transportation Enthusiast

". . . If you have links that better define your position, then please provide them, otherwise I am going to put the text back in."

If you replace the text as you had it, then I shall remove it. "Cherry-picking" of links to support one's position (even if "quoted directly") should not be acceptable on "Misplaced Pages."

1.) There are, at most, several dozen U.S. urban-suburban corridors with passenger traffic density sufficient to justify the investment required for "light rail" development. By contrast, there are at least several hundred urban corridors with sufficient traffic density to justify some level of investment for improved bus service.

We have stated this point repeatedly; you might wish to read "Beware of LRT Oversell" on www.publictransit.us.

2.) I assert that you have included Michael Setty and myself among your betes-noir only because we have chosen to speak out against your preferred technology "per se.". We have made clear our reason for doing so. We believe that "alternative" transportation technologies - such as PRT - have only limited scope in the U.S. because U.S. transportation problems are almost always sociopolitical and economic�not technical�in nature. You might wish to read "Conventional Rail vs. 'Gadgetbahnen'� on www.publictransit.us.

You do not state that the views of the other X000 transportation professionals in the U.S. are not known. Instead, you lash out at us without bothering to represent our viewpoint accurately (which, once again, is that U.S. transportation problems are almost always sociopolitical and economic - not technical - in nature).

3.) I have no intention of engaging in a PRT "safety analysis" because I have no intention of second-guessing either the California Public Utilities Commission or Japan's Ministry of Land, Infrastructure and Transport - nor other jurisdictions which might follow the examples of California or Japan. Yes, the rules might change but that is a moot point because it is self-evident.

". . . PRT would not be certified under current regulatory law in ."

You need to include the above to "follow" the theoretical discussion of PRT safety issues - and I urge the mediators to take note of this in particular. In fact, you also need to mention that Japan did not certify PRT during the mid-1970s.

Ldemery

Do you really believe that the current regulatory environment is all that needs to be said regarding PRT safety? No technical arguments, no engineering analysis, just: "the rules forbid it, so it can never happen"?

You know perfectly well that regulations are based on analysis of known systems. To say that existing regulations supercede real analysis of new systems is irresponsible and unethical, especially coming from a transportation consultant such as yourself.

It's like arguing that an airport can't be built because planes exceed vehicular speed limits on runways!

Laws change to reflect changes in society, and regulations change to reflect advancements in technology. You should know that, and the mere fact that you are advancing this argument is an indicator that you would rather suppress this technology than evaluate it.

In any event, I did notice that you removed yourself from the Cons section (which had been added by user Avidor, aka PRTskeptic) as well as from the Pros section. The only reason I added the text about you to the Pros section was because I believed that Avidor's paragraph about you was misleading, since he included nothing about your admitted bias against PRT. It was Avidor who was "cherry picking" your views, not I; my text just filled in the blanks left by Avidor.

So, now that I realize that you also removed Avidor's Cons text, I have no problem keeping the Pros text out. A Transportation Enthusiast

"Do you really believe that the current regulatory environment is all that needs to be said regarding PRT safety? No technical arguments, no engineering analysis, just: "the rules forbid it, so it can never happen"?"

I did not say that, and please don't put words in my mouth. Your emotional POV regarding changes in laws to reflect changes in technology tends to suggest that you wish to suppress the (apparent) facts about the current regulatory climate rather than confront the facts.

Once again, I urge the mediators to take note of the following - which needs to follow the "theoretical" discussion of PRT safety issues.

". . . PRT would not be certified under current regulatory law in ."

("Apparently" appears a reasonable choice of words re. California, if not for Japan.)

You will also need to mention that Japan did not certify PRT during the mid-1970s.

Ldemery

"I did not say that, and please don't put words in my mouth. Your emotional POV regarding changes in laws to reflect changes in technology tends to suggest that you wish to suppress the (apparent) facts about the current regulatory climate rather than confront the facts."

OK, just to be clear then: you are saying that current regulatory law does not imply anything about the safety of PRT (or lack thereof), and that those regulations are likely to change if PRT is shown to be safe after engineering analysis and testing?

I'm not trying to put words in your mouth; I'm just attempting to understand your exact position on PRT. Honestly, even after reading your website, it's difficult to understand exactly why you have taken such a strong position against this technology. Even when you speak against it, you talk more about monorails and maglev than PRT, which is fundamentally different from those other modes.

You've pointed out your article on the problem being sociopolitical and economic in nature (I assume you mean this but correct me if I am wrong). Yes, I've read that article, but it still says very little about your PRT position, other than that you are against it.

PRT is only mentioned in passing in that article. You discuss monorails, maglev, even BRT, but barely touch PRT. I quote: "In our view, it is a big waste of time advocating such "gee-whiz" options, given the severe limits of monorails and similar technologies such as PRT." The clear implication here is that PRT is dismissed solely on the basis of being "similar to monorails" when in fact monorails are much more like light rail than PRT.

If you do have a more extensive argument against PRT, I am very interested in seeing it. But, dismissing it solely on the basis of its presumed similarity to monorails is vague at best, misleading at worst. PRT is nothing like monorails or maglev trains.

By the way, feel free to add the text about Japan and California yourself. That's what Misplaced Pages is all about. A Transportation Enthusiast

As invited, I have described the "certification" or "licensing" issue making specific reference to Japan and California. I have put this under "cons" because, as outlined, the technical feasibility of PRT is a separate issue from whether regulatory agencies would approve (license) such a system to carry passengers. Ldemery 22:46, 15 February 2006 (UTC)

This looks good to me. You might want to link to your research document about CVS in the section about Japan. A Transportation Enthusiast

As invited, I have added a link to my Japan Automated Guideway Transit paper (as explained therein, Japanese AGT has a strong PRT heritage), and to the statement from the California Public Utilities Commission. Without attempting to second-guess CPUC (because no PRT system operator has yet applied for CPUC certification), I think it reasonable to point out the uncertainty about the degree to which CPUC would hold PRT to "light rail" and "rail fixed guideway" safety standards.

I have simply added the following sentence:

"The degree to which CPUC would hold PRT to "light rail" and "rail fixed guideway" safety standards as a condition for safety certification is not clear."

Ldemery 22:46, 15 February 2006 (UTC)

Mr. Demery: Your points about regulatory concerns are very fairly presented. I apologize if I appeared hostile to your concerns earlier -- things have been a little tense around here lately. A Transportation Enthusiast

Politics of PRT

There should be a section on politicians that have promoted PRT like Michele Bachmann. Misplaced Pages has a page on Michele Bachmann. Avidor 16:03, 15 March 2006 (UTC)

Should have something on Dean Zimmermann too. Today's DZ news: Avidor 18:17, 15 March 2006 (UTC)

Go ahead and put that on. Fresheneesz 00:10, 19 March 2006 (UTC)

Vote to ban User:Avidor from editing

I propose a vote to ban User:Avidor from editing this page, or anything on wikipedia, whichever is easier. Avidor has proven time and time again that he simply hates PRT, and almost all of his edits are vandalism. His rants are filling up this discussion page like nobodies business, making it hard for people to sort through the mess.

I also propose that following this vote, we give Avidor one last strike before we find an admin to finish the job.

Votes For:

• If Avidor can bring himself to be more diplomatic and restrained, I'll transfer my vote to votes against Fresheneesz 08:29, 20 March 2006 (UTC)

I'd like to point out that, since you've called for this vote, Avidor has edited the main page twice and this talk page once; and none of these edits are what I'd consider constructive. I think it's safe to say he's not going to take the diplomatic, restrained route. A Transportation Enthusiast 03:08, 21 March 2006 (UTC)

• I vote to ban from editing this page. He has repeatedly demonstrated that he has no interest in debate or facts, and that his promary goal is to manipulate this article for his own propaganda purposes. It's been almost two full months now since he originally challenged this article, and he shows no sign of changing his tactics. It's also been almost a year since his first vandalism, at which time he replaced the entire article with his propaganda pitch. I'm against giving him another chance, because he'll just tone it down for a week and then come back and vandalize again when nobody is looking -- he has a history of doing this. I'd also like to point out that I and others tried to engage him in debate countless times, and he just ignores us in favor of his propaganda pitch. (side note: I haven't logged in for over a month, but I am IP address 72.65.19.184) A Transportation Enthusiast 12:14, 20 March 2006 (UTC)
• Ditto. 99% of the time, his edits are vandalism. I do of course think it is necessary to portray, in an NPOV fashion, the criticisms and controversy surrounding PRT -- however, Avidor's psychotic interjections hardly qualify. It is clear to me that his convictions and his actions are based in mental illness rather than reason, and I therefore see absolutely no point in attempting to reason with him any further. He should be banned from posting, and moreover, the noise he has created on this page should be removed to a archival sub-page. Skybum 16:26, 20 March 2006 (UTC)
• Look at his contributions. He hasn't contributed significantly to Misplaced Pages except for the discussion here and the vandalism on the article page. He has no interest in debating the topic rationally. Non-poster 22:47, 20 March 2006 (UTC)
• Aye. I congratulate all of you for your patience, I am amazed it has lasted this long. Mr Grant 23:39 21 March 2006

Votes Against:

Avidor has been warned

Voting can continue above. After his next act of vandalims, and if the vote is still passes, he will be recommended for being blocked. Fresheneesz 19:36, 21 March 2006 (UTC)

Avidor just re-applied the NPOV tag, calling the article wacky and its authors cultists. I think this should do it, right?

Yea, that does it. Fresheneesz 23:47, 21 March 2006 (UTC)

He's not far wrong, though, the article is 50% blatant promotion and 50% hyperbole. And I speak as a massive fan of alternative transportation. Surely we can make this article better than it is now? Just zis Guy you know? 17:12, 23 March 2006 (UTC)

I agree that it is a very messy article, and could use substantial revision. However, this is virtually impossible to focus on while fending off a barrage of vandalism, which is what 99% of Avidor's edits were. As for your charge that the article is "blatant promotion" and "hyperbole" -- I'm sorry, but I believe that you're wrong. Reporting the claims of PRT proponents -- provided they're portrayed as "the claims of PRT proponents" and not "facts" -- is neither promotion nor hyperbole: it is, in fact, good NPOV reporting. If you can find anywhere where such claims are misrepresented as facts, however, I would absolutely welcome any fixes that you would care to make. Of course, there are also such things as actual non-subjective facts about PRT, as established by various current and historical attempts to implement it, and I believe the article does a reasonably good job of sourcing those facts. Again, if you find anywhere where a factual claim is either innaccurate or un-sourced, please fix it. Really, I mean it. I would be desperately happy if a hitherto-uninvolved party went over this article with a critical, rational, fine-toothed comb. Unfortunately, simply labeling the whole thing as "promotion" and "hyperbole" doesn't accomplish anything at all, as it is both untrue and un-actionable. Skybum 18:20, 23 March 2006 (UTC)

Skybum: I agree completely. We really want to make this better, but it's tough not knowing specific, actionable items to work on.

To "Just zis Guy": Read this talk page. When he's raised valid, specific concerns, we've addressed them immediately. The problem is he seems to be intentionally vague so the article remains under dispute. He seems to want the article to remain in dispute.

If you see specific issues, maybe you can help us to make it better. Can you give examples of hyperbole or promotion? I should point out that Louis Demery (a vocal anti-PRT transit professional) has made a significant contribution (in the "Cons" section) that has not been touched by anyone here -- because it's accurate and fairly presented. A Transportation Enthusiast 18:29, 23 March 2006 (UTC)

Neutrality is not achieved by merely placing the opposing views adjacent to each other, though, is it? Anyway, I will be more specific, I will try to go through it line by line this evening. Incidentally, if Avidar does edit-war I will stop him. Just zis Guy you know? 18:36, 23 March 2006 (UTC)

Thank you; I appreciate it! Skybum 18:42, 23 March 2006 (UTC)

I agree wholeheartedly with the statement that "neutrality is not achieved by merely placing the opposing views adjacent to each other". But this approach was taken at the suggestion of the cabal mediator! I was of the opinion that arguments should be interspersed, but with Avidor around it turned into a turf war (i.e. "You can't edit my Cons section!") and the mediator seemed to encourage that.

BTW, I also appreciate you examining this article with a neutral eye. If the article can be improved I'm all for it. A Transportation Enthusiast 19:00, 23 March 2006 (UTC)

Vote completed - pending: talk page clean up

Avidor has been listed for being blocked. I think it would be a good idea to clean the talk page of some of his edits, to an archive. Whoever does this task should try to keep some of his more meaningful suggestions and ideas. Fresheneesz 23:47, 21 March 2006 (UTC)

Note: I've removed the request for mediation. It's been 2 days and Avidor has not yet completed the arbitration request process (if you go to the arbitration page, they currently have nothing on PRT). Having it here was just confusing.

Avidor can re-insert the RFM if/when he completes the formal request. A Transportation Enthusiast 05:29, 23 March 2006 (UTC)

PRT Business Plan

Shouldn't this be included in the article?

From the "Higherway" PRT site

Relocation of Avidor-related text

Per community concensus, I have moved virtually all the Avidor-related text to Talk:Personal_rapid_transit/Avidor. Skybum 18:37, 23 March 2006 (UTC)

I have just removed more of Avidor's ranting to his sub-page. He is NOT welcome here any more. Skybum 16:13, 24 March 2006 (UTC)

Massive Rewrite Needed

Okay, it seems that all sides (to wit: pro-PRT, anti-PRT, PRT-neutral, sane, and "other") agree that the PRT page is a mess, and needs substantial revision. I agree. Most problematic, it seems to me, is the article's overall structure. For example, many of the technical aspects of PRT -- braking, speed, et cetera -- are filed under the heading of "Capacity Utilization". While all these things certainly do affect capacity utilization, they affect many other aspects of PRT system design as well. This kind of hierarchy seems rather arbitrary, and leads to a lot of redundancy in the article.

Therefore, I would like to propose that the article be fundamentally restructured into the following sections:

1. Overview (basic description &comparison with other transit modes)
2. History (needs attention, but is already roughly appropriate, category-wise)
3. PRT system design (technical aspects, noting disuputes & variances between different systems where appropriate)
   1. Vehicle characteristics (size, features, propulsion, safety features, et cetera)
   2. Guideway characteristics (supported vs. suspended, rubber-on-concrete vs. steel-on-steel vs. linear induction levitation, et cetera)
   3. Operational characteristcs (speed, headway distances, control algorithms, passenger security, et cetera)
   4. Cost characteristics (historical & estimated)
   5. Urban Integration characteristics (public acceptance, aesthetics, sociological & urban planning impacts, compatibility and/or competition with other transit modes, et cetera)
4. The PRT Debate (aspects of the PRT debate which are NOT about the technical minutiae detailed above; ie the politics of PRT support and opposition.)

Organized, the article would probably be much less redundant (and hence a lot shorter) than it presently is. Currently, the "pro" and the "con" aspects are in monolithic and essentially non-interacting blocks of text. Shown this way, it is difficult for one to get a sense of how those arguments actually relate to the particular details that they are addressing. By bringing the pro-and-con aspects down to the level of those details, their arguments will be much more contextualized and comprehensible. What do you folks think? Skybum 03:50, 24 March 2006 (UTC)

Okay, it's been a couple of minutes now, and nobody has responded yet. That, and I've got actual work that I ought to be doing, and am thus desperately seeking a way to procrastinate. Therefore, I shall "be bold". I have reorganized the article -- everything except for the "pro" and "con" section -- roughly into the hierarchy described above. I haven't attempt to synthesize the text at all; it was just a rough cut-and-paste hatchet job. So, it's a total jumble now, but honestly, it was a total jumble before. Now at least it's in piles which make some kind of sense, and can hopefully be organized into something better. I hope that you all approve. Skybum 04:31, 24 March 2006 (UTC)

Hey, Skybum, I like what you're doing so far. The tentative outline above looks good. And I've just done a quick scan of your recent overhaul, and I think it's an improvement. Maybe if I get time this weekend I'll scan it more thoroughly and see if I can make some improvements. But I think you've done a great job getting this started. That's a tough task, reorganizing an existing article without starting from scratch -- you seem to have gotten the effort off to a flying start.

BTW, I disagree with you that the article was a "mess". Sure, some parts of it were not organized very well, but I thought the individual points in the article were solid and well presented. It just needed someone bold enough to take on the reorg task. :-) A Transportation Enthusiast 05:52, 24 March 2006 (UTC)

Thank you! I do think there was a lot of good information there; it just wasn't structured well. This made it very difficult to improve, I think -- it was never obvious exactly where any improvements would fit in. But hopefully my edits have begun to clear that up. I'll keep going later this evening; for the time being, I think that most of what I'll be doing is consolidation and compaction. Skybum 17:14, 24 March 2006 (UTC)

JzG's Revisions

Thanks for taking an interest in this. I think your intro revisions are largely an improvement, with two qualifications. First, I do think that there should be some mention, in the intro, of why proponents are interested in PRT (ie, "Proponents believe that PRT would be better and cheaper than existing transit modes"), since this is a key point of the article. It does not quite seem quite neutral to remove that part, while still leaving in the reason why its opponents doubt it (ie, "it is largely unproven").

(Oops--never mind about this concern. I glazed straight over where you did show its proponents claims. Apparently, I haven't drunk my coffee yet this morning. :-). The concern below still stands, however.) Skybum 17:34, 24 March 2006 (UTC)

Second, I do have an issue with calling it "largely unproven". Keep in mind that the Cabintaxi system, in the late 1970s, had a network with 6 stations and dozens of small vehicles. It operated in point-to-point mode at short headway distances (1-3 seconds), demonstrating rapid switching, ad-hoc routing, and vehicle safety for over 400,000 vehicle-miles. This experience (along with ULTra's, less extensively but more recently) proved every single technical aspect of PRT. From an objective, neutral point of view, there simply cannot be any argument about that. This does leave many critical non-technical aspects of PRT unproven, such as public acceptance, vandalism rates, operational costs, insurance costs, regulatory issues, actual ridership share, et cetera. Thus, I think it's fair to call PRT "largely unproven in a real-world installation". But simply leaving it at "largely unproven" is overly biased to the negative. The analogous situation would be if, in Fusion Power for example, an expensive experimental reactor had successfully demonstrated a sustained reaction with a power surplus, but no reactors had yet been mass-produced and hooked up to the grid, so its economic viability was still an open question. In that situation, idividual reactor designs could still be called "unproven", and the entire field could be labled as "unproven in the market". But the concept itself could no longer be called "unproven," and neither can PRT.

Despite the above concerns, I'm going to leave the intro alone for a while, and see what else you do with it. I am very glad to have some new blood working on this article; thank you again for getting involved! Skybum 17:14, 24 March 2006 (UTC)

Question: why are you removing citations which link to the Innovative Transportation Technologies website? Despite its questionable HTML, that website is the definitive academic reference for advanced transportation technologies (PRT and otherwise). It is administered by professor Jerry Schnieder, but I would not call it a "personal web page".Skybum 23:01, 24 March 2006 (UTC)

I am removing a lot of external links, per WP:EL. We can cite sources at the end, once per source, in line with ususal practice. I think the text is better than it seems superficially, it's mainly good solid stuff but stated rather enthusisatically. I'm not going to be drawn on the Avidor business, partly because he has a valid point and partly because I am a huge fan of Road Kill Bill - it's grade one cyclist agit-prop :-) I'm confident that we can make this better, sharper and more neutral with relatively little effort.

Incidentally, my background is electrical engineering although I now work in IT, I'm a railfan and a railway modeller, and I have a good deal of enthusiasm for light rail and other alternative transport modes. I take my Brompton Bicycle on the train to work most days - that's what I calkl personal rapid transit, I can get to the station in about half the time it takes the cagers :-D. Just zis Guy you know? 23:26, 24 March 2006 (UTC)