Is CPT PRT-Able?

Post by Steven Dale

David asks:

PRT is getting some buzz lately what with Heathrow’s system going live soon and Masdar in the works. Do you know of any systems or engineering solutions that allow overhead gondolas to work the same way? IE: Swap to a different cable at a junction? Is CPT PRT-able?

Swapping to a different cable at a junction is possible as the industry has already developed and implemented automatic sortation devices for their systems. That technology could be adapted to a configuration like you’re talking about.

The important thing to remember is that while cable technology is old, it’s application to urban transit is quite new. The industry is just now learning about public transit and what their technology can do.

A great example is Medellin, Colombia. When their first CPT system opened in 2006, it could carry 3,000 pphpd. At the time, that was the maximum capacity any modern cable system had carried.

The day it opened, however, it was over capacity by almost double. The cable industry had never dealt with numbers like that. A direct result of that experience, has been the industry’s development of new technologies that allow 6,000 (aerial) and 10,000 (terrestrial).

For CPT to catch on, it’s important for people to ask questions like this so that the industry can develop solutions to problems it doesn’t know it has.

CPT is in an adolescent phase. It’s basically a teenager. It has all this potential and numerous accomplishments, but needs help being pushed in the right direction for it to fully realize its potential. You can be certain if the market begins to demand line-switching or very high capacity systems or very long line lengths, the industry will develop that.

Also: Some might disagree with me, but the Heathrow system is not PRT. It is simply small automated vehicles in a linear arrangement with off-line stops. One of the major components of PRT (in theory) is the complex network component. The Heathrow system simply does not have that component.

In fact, no system that calls itself PRT has ever had that component. I’m not saying it won’t happen, and there are rumors that it may be added in later at Heathrow, but as of right now, it’s nothing more than a people mover. As for Masdar, I honestly don’t know enough about that installation.

So . . . long answer to a short question: Theoretically CPT is PRT-able. At the same time, PRT is theoretically PRT-able, yet ironically, PRT has never demonstrated itself to be PRT-able.

Are you as confused as I am now?

Speaking of Medellin, tune in tomorrow for the start of The Gondola Project’s first photo essay on the MetroCable systems in Medellin, Colombia and Caracas, Venezuela. Tell your friends!

Want more? Purchase Cable Car Confidential: The Essential Guide to Cable Cars, Urban Gondolas & Cable Propelled Transit and start learning about the world's fastest growing transportation technologies.

Want more? Purchase Cable Car Confidential: The Essential Guide to Cable Cars, Urban Gondolas & Cable Propelled Transit and start learning about the world's fastest growing transportation technologies.


  1. ULTra is a PRT technology. Even though the guideway between LHR Terminal 5 and a satellite carpark is a line, it is technically network because there are three stations and the pods don't have to stop at every station. In addition, at 3:10 of this video there is a diagram showing how the BAA company would like to expand ULTra to other terminals, hotels and facilities. It will then 'look' more like a network. http://www.youtube.com/watch?v=epiiPy9kAho Other leading PRT technologies include Vectus.se (Sweden/Korea) and 2getthere.eu (Masdar City).
  2. Oh, I should add that the current ULTra route looks like a single line, but it should be viewed as a loop that has been squeezed so that the two long sides happen to be in the same right of way.
  3. David, That's part of the controversy of PRT. What is or what is not PRT? Most definitions of PRT tend to include the concept of a complex network of stations. A simple single line with 3 off-line stations would not fit it with that traditional definition. There's really very little special about it. At the same time, PRT has to start somewhere and a single line makes most sense. Should Heathrow expand the system into a complex network as planned, then yes it would be PRT. Everyone's entitled to their opinion, but as I see it, London Heathrow does not currently qualify as PRT.
  4. For more on Personal Rapid Transit (videos, links, studies): http://www.prtstrategies.com.
  5. FYI, here is the generally accepted definition: http://faculty.washington.edu/jbs/itrans/PRT/Background.html
  6. David, I think what we have here is a situation where your "generally accepted" definition is different from my "generally accepted" definition, and I'm not sure we'll be able to resolve that. From Dr. Vukan Vuchic, author of Urban Transit: Systems and Technology: PERSONAL RAPID TRANSIT (PRT) - An imaginary transit mode consisting of small-capacity (two to six spaces) cabin-type vehicles traveling automatically over an elaborate system of guideways; individuals or small acquainted groups would use a cabin to travel between origin and destination stations without stopping. The concept is hypothetical and not feasible in the real world. Do I agree with Dr. Vuchic's definition? Not entirely. But I also don't entirely agree with the definition you've provided either. That the definition you provide suggests that PRT can include vehicles of up to 100 riders throws into question the entire definition itself. After all, how can it be "personal" if one has to share a vehicle with 100 others? The fact that it totally ignores the network issue is also suspect. The London Heathrow system is roughly 5 km long with 2 terminals and 1 intermediary station in a linear arrangement, if I'm not mistaken. At most, a rider would not have to stop at that single intermediary station, creating a time savings of roughly 1 minute. I hardly see the advantage here. If the system is successful (and I hope it is) and greater network capabilities are added in the future, then I'm all for it. My issue with Heathrow right now is that it is not PRT. Clearly we disagree on this point, but until a greater network component is added, I don't see how your classification works. After all, if I was riding a fully-automated light rail system by myself and was thus able to miss each stop in between my origin and destination because of a lack of other riders, could I not also call that PRT? Or what if I was riding in a PRT vehicle at Heathrow with a friend of mine, and she wanted to get off at stop 2 and I at stop 3? Suddenly I'm not by-passing stations. Should I continue to call that PRT? The essence of PRT is not the small vehicles - those are easy. The essence of PRT is non-linear, network capabilities, and that's hard and expensive. Heathrow does not have that and until it does have that, I don't see how it (or any other system) can reasonably call itself PRT. I'm skeptical right now, and that's healthy. Instead of trying to ram Heathrow down everyone's throats by calling it PRT (which it clearly isn't), the PRT movement would be more successful if they celebrated it as a step towards PRT. But then again, that's just my opinion.
  7. For me PRT should have similar capabilities like a car. And it will have most benefits and disadvantages of cars. I even think if we have PRT somedays it will be evolved from cars rather than from downsizing Rapid transit technologies. The Heatrow system is a good example the vehicles are basically electric taxis with a robot driver. this we can call it PRT as the technology allows expansion of the network.With the advance in electronics,IT and AI we can even imagine that within two decades we will have automated vehicles mixing with human steered traffic. On the other side a chairlift or a two person gondola is not PRT as the technology does not allow complex networks (yet).
  8. At the same time, PRT systems don't offer complex networks either. Maybe in the future, but not right now. At the same time, given advances in computer-controlled driving systems, we should ask ourselves what the role of transit is, in general. Maybe everything we're talking about is moot. Maybe in 50-100 years all our cars will be computer-controlled in some complex hive/swarm system. Maybe public transit, whether it be PRT/CPT/LRT/BRT/HRT is not long for our world. Who knows.
  9. "Up to 100 riders" is the definition of APM. The material at the link was written to differentiate the PRT subcategory from the larger APM category. Scroll down, note criterion 3, and also follow the link at the bottom! How complex does the network have to be before you would allow it to be called PRT? PRT designers are purposely designing their systems to fit a number of niches -- shuttle, feeders to train stations and circulators -- in addition to general transit duties. One must also consider that the newness of these newer systems means they are more than likely to be piloted with smaller applications like Heathrow. Even the planned citywide Masdar PRT is starting with a small initial phase. By your reasoning, even when these and other small PRT phases get started PRT will still not 'exist'. Thus, I really disagree that PRT means complex topology -- rather, it means having the capability for such complexity. An automobile on an island with only a mile of road is still an automobile. Light rail is still light rail even when it's only 1.6 miles long (ie Tacoma). The 1.2 mile Seattle monorail is still a monorail. Let PRT be PRT.
  10. Here's a satellite image of the parking lot end of the Heathrow PRT system: http://www.bing.com/maps/?cp=51.47962~-0.48698&lvl=19&style=a The two parking lot stations are on separate loops rather than a single line with an intermediate station.
  11. David, I apologize, I did read that wrong (re: the 100 riders issue), I take back that comment. At the same time, you asked me to "scroll down . . . and follow the link at the bottom." Well, I did, and within that link at the bottom was this comment from the website you directed me to:
    there is no PRT system currently in operation anywhere in the world.
    What am I to do with that? As for your monorail, light rail argument: The point about Tacoma and Seattle is false. The Tacoma Light Rail system is light rail because it meets the definition of light rail, just as the Seattle monorail is a monorail because it meets the definition of light rail. The definition of those technologies do not include a clause regarding line length. The London Heathrow is not PRT because it does not meet the definition of PRT. I'm not stopping PRT from being PRT, PRT is stopping itself from being PRT.
  12. Ken, Thanks for this. Can you explain why it is that so much infrastructure is required for a simple branch configuration. This is basically just a T-shaped intersection, but it seems from the image you provide that a huge amount of infrastructure is used to accomplish this. How much more track infrastructure would be required in a more complex network? Steven.
  13. I'm not sure which parts you might be including as "huge". In this area, the lighter guideway is elevated and the darker, blacktop guideway is at ground level. I'm assuming they "squeezed" the ground level loops to avoid blocking lanes of traffic through the parking lot. That's what makes this area look like a T rather than a larger loop. The stations are the two rectangles towards the top of the photo. There are two guideway sections in front of each, the guideway nearer the station is the offline portion and the guideway further is the online or non-stop portion. These would be typical of any station in a more complex network. The building on the left loop is the service and maintenance building for the network. There'll be at least one of these in any network. On the right loop is an additional section of guideway for storing extra vehicles. These are used for both overnight storage of unused vehicles and for staging empty vehicles near areas of demand. These would be found occasionally in a larger network. Lastly, this is an "one way" branch loop configuration: outside of the offline station sections there are never any locations where a vehicle is moving in a direction opposite or across the path of any other vehicle.
  14. Ken, I understand all of that. What I more mean is the huge amount of infrastructure in the centre of the 'T'. The 'Big O' Let's call it. What I'm asking is this: Is the 'Big O' required for this configuration to work? Is this the extra guideway for storage of vehicles you mention? Is it logical to store your transit vehicles outdoors in the rain? In London? How efficient is a technology that needs such infrastructure just to move 21 vehicles (because that's all this system currently uses) through a T intersection? That's all I'm asking. And how big of an O or Figure 8 or Zig Zag, or whatever is going to be required to move hundreds of vehicles through a complex network? This is what the PRT industry has not been able to effectively explain to people. Also: Why does there need to be an off-line/on-line section of guideway at the two stops? If I look at the map carefully, the only reason that a vehicle would have to be in either of the station loops would be to actually stop at the stations. Why then would it require an off-line component at all? That, I'm legitimately asking. It just doesn't seem to make much sense. What am I missing here?
  15. The "Big O" is not required for this type of configuration as far as I know. The parking lot area could have been one single loop. My best guess would be that the "Big O" and on-line sections of guideway are there to provide as "real" a final system as possible in the initial operations testing. The storage guideway is one of the two parallel guideways on the "bottom" side of the right loop. Here's the most fully-reviewed and published design proposal for a more complex PRT network I'm aware of: http://skyloop.org/system-networks.htm#SkyLoopNetworks There's very little additional infrastructure between loops. That SkyLoop design was for 700 vehicles.
  16. So then the Big O would be required for a more complex network?
  17. No. By "real" I meant representative of a larger network for testing.
  18. The Original David
    I hate it when people on the same side fight...I think we all aspire to a future beyond trains, trams, buses and particularly cars. I see gondolas as having great potential for cost and visual intrusion reasons, and wanted to explore the possibilities. My original question was whether gondola technology existed for switching between cables which would allow a PRT-esque travel experience. I understood the answer to be that this technology has been developed for industrial uses but would need to be adapted for passenger applications. The corollary answer was that PRT technology for both cable and non-cable systems was in its infancy, with driverless theme-park-style cars being the most advanced form at present.
  19. Couldn't agree more, Original David.

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