Posts Tagged: PRT

06
Dec

2011

One of the Best Analyses of PRT You’ll Ever See

Image via swiftprt.com.

We here at The Gondola Project tend to be a pretty open-minded group of individuals with our readership generally following suit. We’re not, however, slaves to fads or trends. When we look at new ideas, innovations and technologies, we try our very best to be objective and analytical about them (but appreciate and love the craziness of things like the Chinese Tunnel Bus™).

We approach things from a position of empirical skepticism. We need to see that something can actually work – or at the very least, that the theory and logic underpinning a concept makes sound and reasonable sense. As a result, we’ve tended not to have a fondness for the mythologized panacea of the public transportation world; Personal Rapid Transit (check here and here for two of our more interesting debates with PRT advocates).

The fundamental logic behind PRT is quite simply flawed with most advocates of the technology blind to the economic and technological limitations of it. But that doesn’t prevent it from being continually trotted out as transportation messiah.

That’s why the work of blogger and researcher Apatzer is so fascinating.

Over at a brand new site called Swiftprt.com Apatzer meticulously (and sometimes exhaustingly) details the 6 months he spent researching and coding a simulated PRT network to investigate the technology’s feasibility.

His basic findings are that PRT is financially unfeasible; is incapable of providing the needed capacity in dense urban environments; and cannot provide the time savings over the private automobile typically sold by PRT advocates and companies.

I won’t go through his entire analysis as that would take about as long as it took him to do his study. As such, it’s hard for us to say whether his work is “right” or “wrong.” But for anyone interested in PRT as a viable urban transportation solution, they should spend a serious amount of time and energy exploring his work.



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Personal Rapid Transit
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20
Aug

2011

Weekly Roundup: Solar Powered Gondolas

Colorado's Telluride Gondola is set to be powered by solar panels with an extensive carbon offset policy. Image by flickr user Glenda Jeffrey.

A few highlights from around the world of Urban Gondolas, Gondola Transit, and Cable Propelled Transit:

  • Could the cable industry be taking aim at PRT? Indian Express reports that the world’s two largest CPT manufacturers – Doppelmayr Cable Car and Leitner Ropeways – have attended a pre-bid meeting in order to bid on a project to build India’s first Personal Rapid Transit system. CPT vs. PRT, this should be an interesting story to follow.


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Weekly Roundup
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09
Feb

2011

The (Il)logic Behind PRT

The Morgantown PRT. Those vehicles sure do look personal don't they? Image by Brian M. Powell.

Personal Rapid Transit (PRT) is a technology that’s been dreamed about in transit circles for roughly the last 60 years with little to no progress. For those unfamiliar, the concept of PRT is based around the following 4 principals:

  • Small, automated vehicles with seating for 2 – 8 people.
  • Vehicles available on demand at stations throughout the system.
  • Direct from origin to destination. Vehicles do not have to stop at intermediary stations.
  • Non-linear networks of stops, thereby eliminating the need for transfers.

The concept is that for public transit to compete with the private automobile, it needs to replicate the comfort of the car. Fair enough.

The transit-geek-gadgetbahn-aficionado in me would of course love to see PRT sometime in my lifetime. But that’s based upon blind hope and little else. The fundamental logic behind PRT just doesn’t work. Here’s five reasons why:

ANY CHARACTER HERE

ONE. Vehicle Capacity. The appeal of Personal Rapid Transit is that it’s personal.

And yet if every vehicle were loaded with only one single rider, there would be plenty of wasted capacity and seats. As a PRT system typically has only one single guideway, the system would basically just be replicating a single lane of under-capacity cars. There is, however, a solution to this problem. Which leads me to my second problem:

ANY CHARACTER HERE

TWO. Solving the vehicle capacity problem negates the whole concept behind PRT.

The only way to solve the problem outlined in the previous point is to enforce a ‘carpool’ mentality. How popular is carpooling? Station attendants would necessarily have to force riders to ‘buddy-up’. 8 person vehicles would be filled by 8 people whether they were traveling together or not. Suddenly it’s not personal. Suddenly you have 8 different people traveling to 8 different locations. Which leads me to the third problem:

ANY CHARACTER HERE

THREE. Station Attendants will cost money.

Any cost savings that PRT imagines would be erased by the need for station attendents to enforce carpooling during peak hours. Despite having these station attendants, it’s unlikely that the attendant will be able to group passengers according to their destinations. As such, we have a fourth problem:

ANY CHARACTER HERE

FOUR. People going in 8 different directions must travel in 8 different directions.

So now it’s rush hour and we’ve got 8 different people traveling to 8 different destinations. Now the algorithm used to control the vehicles must calculate a linear route that stops at each destination sequentially. And that would be utter insanity. Imagine if you and your fellow rider were traveling to destinations at the exact opposite ends of your respective city!

You could solve this problem by giving everyone their own vehicle, but to do so leads us straight back to point ONE. The only real way to deal with this issue is to institute fixed routes, which leads me to the fifth problem:

ANY CHARACTER HERE

FIVE. The Appeal of PRT is the Elimination of Fixed Routes.

If suddenly every PRT system is a linear fixed route, then what we have is nothing more than an Automated People Mover that has the ability to skip stations. Note, however, that as 8 different people with (presumably) 8 different destinations are using this souped-up APM, riders will still be faced with the situation of stopping at stations different from their destination.

It shouldn’t surprise anyone that the most famous “PRT” system in the world is the Morgantown PRT in Virginia -which shares a surprising resemblance to the situation I’ve just described.

ANY CHARACTER HERE

SIX (BONUS!). Google’s already invented PRT.

It works and is a driverless car.



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Personal Rapid Transit
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22
Sep

2010

Pod Cars Start To Gain Traction

Yesterday, the New York Times ran a piece titled Pod Cars Start to Gain Traction in Some Cities.

The author, Jim Witkin posits this basic question: Is PRT finally ready for prime time?

The article is scant on details but suggests that London Heathrow’s PRT pilot system is evidence that the technology is ready to be deployed throughout the world. Problem is, the technology is no where near “ready for prime time.”

According to the article, the Heathrow PRT system includes 21 vehicles, 3.8 km of elevated track and will carry 1,000 people per day. Per day. For comparison purposes, the Medellin Metrocable moves approximately 40,000 people per day over its 2 km of guideway.

For whatever reason, people love to debate the merits of PRT and the Heathrow system ad nauseum (see the comments on this post for just such a debate). I suspect it has to do with the ideological fervor PRT advocates possess and the natural cynicism that accompanies such fervor.

But absent from much of the debate is this: The Heathrow system doesn’t work.

Construction on the Heathrow PRT was completed in mid-2008 when testing began. Fast forward two years later to today and the system is still not open to the public and there doesn’t appear to be any consensus about when it might be. (A fact strangely missing from Witkin’s article.)

Until this (or any other PRT) system can demonstrate its functionality in a pilot program or other environment, PRT will continue to be nothing more than the public transit technology of the future – a designation its held for the last 60 years.



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Personal Rapid Transit
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10
Dec

2009

What about PRT?

Personal Rapid Transit (PRT) is a theoretical transit technology, the theory being that in order for public transit to compete with the private automobile, it must mimic the attributes of the car.

Just like a car.

Just like a car.

PRT is typically imagined to have the following attributes:

1. People ride in personal vehicles of up to 4 people.

2. Vehicles are available on-demand.

3. Vehicles travel (typically) on a network of elevated guideways.

4. Off-line stations mean there is no need to stop at intermediary stations or transfer between lines.

PRT is admittedly appealing, but I think it’s mostly smoke-and-mirrors. The technology’s embrace of off-line stations is also admirable, but somewhat misguided. The appeal of off-line stations is that vehicles don’t need to stop at intermediary stations, thereby increasing overall travel speed. The trouble, however, is the need for a huge fleet of self-propelled vehicles to accomplish this feat. To achieve the same result with current rail (or maybe Cable Propelled Transit) technology, one would only have to mimic (and reverse) a technique used in 19th century known as coach slipping.

Coach Slipping.

Coach Slipping.

Could PRT be the transit technology of the future? Sure, why not? I try really hard in my work not to be partisan and if PRT were successfully demoed I’d be the first to jump behind it. After all, I’m the guy that thinks we should commute to work in ski lifts.

Trouble is, PRT has never actually been demonstrated. The idea is over 50 years old and it has never once been implemented. Systems at the University of West Virginia and London Heathrow call themselves PRT, but are in fact, not due to their lack of network capabilities. They are really, just small vehicle people movers.

Some day, PRT may happen and, if so, great. But I doubt it. After all, we already have Personal Rapid Transit. We just use the terms “cars,” “feet,” and “bicycles” instead.

What do you think? Is PRT the technology of the future?

Creative Commons image by Skybum



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Analysis
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