Thursday, June 6, 2013

Op-Ed: Is Personal Rapid Transit the Future?

In the deserts of UAE, some 11 miles southeast of Abu Dhabi, Masdar City is envisioned as a sustainable, zero-carbon, zero-waste ecology, with complete reliance on solar and other renewable energy sources. The city will be home to around 50,000 people and is expected to cost $22 billion to construct. So, what does transportation look like in the world’s first zero-carbon city? Well, the city is designed to be completely car-free and given that it is one square mile in size, it is probably an achievable goal. An important element of this city’s transportation vision is the Personal Rapid Transit (PRT) prototype. This op-ed will explore the role of this recent technological innovation in a city aiming to be completely sustainable. Additionally, I’ll discuss the PRT system, and its potential applications in urban environments.

Masdar City’s pedestrian-focused, walkable design showcases continuous shaded areas for walking and human-scaled urban design features. The city’s transportation system is made up of electric cars, electric buses and the PRT pods buried underground. Masdar City’s PRT system has attracted much attention, as it was one of the only systems in the world designed on such a large scale. A light rail line and Metro lines will eventually connect the city center to Abu Dhabi. Cars are not allowed inside the city but are limited to parking lots at the edge of the city, close to future light rail lines.

So, what is Personal Rapid Transit, anyway?
It is an emerging transportation mode that uses small, computer-guided ‘podcars’ to move groups of 3-6 people between stations on a dedicated network of guide-ways. These vehicles are driverless and operate on-demand, eliminating the need for actual cars. Since the PRT systems are computerized, the cars can by-pass crowded stations, reaching its destination in an efficient manner. Currently, there is a working prototype in Masdar City; the city had to be lifted on a pedestal to accommodate the PRT.

Although there are a few PRT systems being implemented, the only other functioning PRT system in the world is in the London Heathrow Airport, known as ULTra (Urban Light Transit) with a fleet of 21 cars on elevated tracks. This system serves as a connector between Terminal 5 and its associated parking lots, reaching speeds up to 25kmph (15.5 mph). Already, this system is being credited with using 50% less energy than the diesel burning buses it replaced.

PRT has enamored many academic endeavors as well. Students at Princeton University produced a report on the feasibility of implementing PRT on a statewide scale! University of Washington has a huge online resource that has the most updated research on PRT and an active debate going on about its benefits.

However, I think their scope is best limited to a smaller scale. I see their implementation to be especially useful on university campuses (1), airports, large hospitals, and neighborhoods – areas that are similar in size to Masdar City and where there is an aspect of self-sufficiency within the campus or neighborhood. This gives rise to the idea of PRT being a possible solution for the last mile issue by serving as local collectors of a light rail line. Andreasson explored this issue in a feasibility study paper and concluded that functions such as ticketing, vehicle scheduling, and station design, were critical to the success of PRT (2).
Can PRT really make a car-free city work?
As fantastic as this idea of a sustainable city, like Masdar City, seems to be, the city itself has been widely criticized as a futuristic, high-end ‘enclave’ that caters only to the rich with many skeptics are calling it the “Cancer City”. Moreover, the extreme costs of expanding the PRT prototype, led the city to scrap the project entirely.

Critics of the PRT are very vocal and their opinions are not limited to its application in a ‘sustainable city’. Tahmasseby and Kattan’s TRB paper outlines some major concerns of PRT. The PRT system has been deemed too small to meet passenger load demands of an actual city, especially in the central city areas. Moreover, there is a dearth of research on its better integration in urban environments – whether it works as a stand-alone or integrated with larger mass transit systems. There are also reliability issues - concerns about performance and emergency situation management in extreme weather. Lastly, it being such a new system and yet to be regulated technology, there is a lack of consensus on whether to apply rail regulations or to apply personal vehicle regulations.
That said, I think the problems arising from PRT are similar to both the electric and the Driverless Car. According to J. Edward Anderson, faculty member at University of Washington, the PRT system, if unregulated early on, has a very real potential to contribute to further sprawl, as the PRT takes away all the inconveniences of a car forcing development to move further out.  Adding to that is their requirement for a whole network of guide-ways that are superimposed on the existing street network, or raised above ground, effectively disrupting visual access and appeal of urban environments.

PRT is a radical solution to an age-old problem. Given that the PRT is such a new technology, it is hard to say what the future will look like. In its current state, implementing PRT in our communities can be extremely cost prohibitive and full of challenges.  They are envisioned to start to solve a regional issue but I think will eventually end up as a specialized local solution, at least until there are huge leaps in innovation, greatly reducing its costs and feasibility issues.


(1) Dr. Shahram Tahmasseby, Dr. Lina Kattan. Investigating economic viability of a personal rapid transit (PRT) system for a university campus and its surroundings. TRB Annual Meeting 2013. July 2012.

(2) Andréasson, I. J. (2012). Personal Rapid Transit as Feeder-Distributor to Rail. Transportation Research Record: Journal of the Transportation Research Board, 2275(-1), 88–93. doi:10.3141/2275-10

Juster, R. (1954). A comparative analysis of personal rapid transit as an urban transportation mode (pp. 1–17).

Alessandrini, A., & Stam, D. (2013). PRT studies in two Scandinavian cities (Vol. 6938, pp. 1–14).

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