New Forms of Mass Transit Gaining Steam

December 17, 2010

Written by Thomas Gonzales

Move over BRT (bus rapid transit)—there are some new faces up and coming in the world of transit technology. Two relatively obscure forms of mass transit, cable-propelled-transit (CPT) and personal rapid transit (PRT), seem to be receiving increased notice and recognition of late and may be headed for greater recognition as new forms of urban transit. Indeed, the first “true” PRT system is getting ready to open at Heathrow Airport in London—where I actually saw it in trial operation last week—and CPT has already found some degree of success around the world in its varied incarnations.

If you’re somewhat of a transportation geek like myself, you may have heard glancing mentions of these two technologies in years past but not seen much concrete evidence of their broader utility.

The first of these two, CPT, is certainly not a new technology and actually can be found operating in numerous locations. Most of us are rather familiar with it in the form of gondolas (seen in ski resorts around the world) and cable cars (the legacy vehicles that remain a popular icon of San Francisco). Personal rapid transit (PRT), on the other hand, has been discussed for nearly a century as a transportation concept, but has seen very little application and acceptance in the real world.








Views of the future? Urban gondolas in Medellín and PRT at London Heathrow Airport.



















In addition to their snowy slope ascents, gondolas and other suspended CPT technologies have actually been built in a few urban settings, such as the Roosevelt Island Tram in New York City or the Portland Aerial Tram. More interestingly, a few South American cities have implemented much more robust suspended CPT systems and incorporated them into their mass transit network; namely, the Metrocable in Medellín, Colombia and the Metrocable in Caracas, Venezuela—both of which are profiled rather extensively by The Gondola Project. Other CPT incarnations, like the “Mini Metro” system in Perugia, Italy more closely resemble traditional, wheel-based forms of urban transportation. Like the fabled San Francisco Cable Cars though, the system’s vehicles have no means of self-propulsion and depend on a continuously moving cable to “grab on” for the ride.

In the case of CPT, the technology has already found its place in niche markets, but new innovations may mean that it’s ready for more broad implementation in urban areas. PRT, on the other hand, is a bit more controversial in its usefulness. Proponents claim it will provide unparalleled service and easy expandability at a much smaller price than other transit systems, while others contend that its transit that feels like a car and therefore has different and negative social implications and effects on the urban environment. Some want to place it in urban downtowns while others think it could only be appropriate for office parks or campuses.

The premise of a PRT system involves a fleet of compact, driverless vehicles that travel along a fixed guideway. The key aspect of the system that differentiates it from other forms of transit is that all vehicles travel directly to their destinations without making stops in between, because each station has a separate pull-out from the mainline right-of-way. In theory, riding the PRT would be similar to riding a sort of direct-express elevator, where the passengers choose only the station(s) they would like to get off at, and they are not bothered by intermediary requests because other vehicles are already waiting at every station for boarding passengers.


PRT vehicles waiting for passengers at Heathrow Airport.


With trials on the first real-world systems underway, the world may soon find out if this form of transportation is a profound, and efficient alternative to automobile travel—or if its touted benefits are simply too good to be true. Based on the slick websites and constructed test tracks of current vendors such as ULTra PRT, Vectus, and others, it seems there’s a fair amount of money and effort banking on the former.

As mentioned in a recent New York Times blog post, PRT systems are being considered at the Mineta International Airport in San Jose, California, which is also where the Podcar City international conference was held at the end of October. The city of Amritsar, in the Indian state of Punjab has also announced intentions to build a PRT system to help circulate devotees and tourists visiting the Golden Temple—an important Sikh shrine that draws more visitors than the Taj Mahal. Overall, India seems to be the country currently most exploring the development of PRT systems.

Advances in technology may be part of the reason these two transit technologies are being taken more seriously and becoming more appealing for integration within existing urban transportation systems. In the case of CPT, that means new work-arounds to allow routes with full 90 degree turns and intermediary stations. For PRT, that means advanced computer controls and lightweight vehicles that ensure the system works as efficiently and safely as promised. Especially in the face of challenging or unusual situations (like the hillside favelas accessed by the South American CPT systems), such innovations could allow for transit systems and their accompanying benefits to be built and expanded at lower cost than with conventional (e.g. heavy or light rail) infrastructure.

Interestingly enough, designers of the auto-free, post-petroleum Masdar City currently planned in Abu Dhabi announced last year that a PRT system of “podcars” would serve to connect areas of the city and complement a light rail system. More recently, it was reported that plans and schedules have been set back, and that the PRT system has been reduced to an “ongoing pilot project.” Understandably, creating a zero-carbon city has proved extremely difficult. Ultimately, it seems that it might not be PRT or other innovations that will make Masdar City so much greener, or as Christopher Choa explained it in an interview with treehugger:

What's green about Masdar City is not the solar cell technology, nor any of the other high-tech features. By far, the greenest characteristics are well known and straightforward: mixed-use, high-density development, incorporating mass-transit.

It seems therefore clear that in the face of new technologies it still remains important to build upon existing principles of transportation and urban design, but who knows what other forms of mass transit (string rail?) may yet prove feasible and useful as we look further into the future.



This article was written by Thomas Gonzales, an intern working with KAI's Baltimore office. He is a senior in the School of Engineering at Northwestern University.






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