Imagine this commute: You leave your office and walk a few blocks to a transit station. An elevator takes you one flight up from the street to a room outfitted with glowing touch screens. It’s rush hour, so people are going and coming, but they’re moving through fairly quickly. At one of the screens, which depicts a map of the city dotted with other stations, you select your destination and swipe a fare card. The computer selects the quickest route between the two points and issues you a number. Glass doors slide open and you step out onto a platform where podcars—small, driverless vehicles—are arriving and departing. One pulls up bearing your number and flashing your destination. Another passenger disembarks and you step aboard. Maybe you are traveling with one or two friends, but not many more than that, because the car only seats six. The doors shut and the pod backs out of its berth automatically, gaining speed along an access way before merging into a stream of traffic—into a gap between two other cars that takes less than a second to close. You don’t notice this feat of coordination because you are sitting back in a plush seat, relaxing, surfing the internet, or just watching the city go by. The car runs along quietly, turning from one elevated guideway to the next. It is driven by electricity and emits no pollution. It bypasses all other stations, never stopping until reaching your destination, where you alight in perhaps a much better mood than if you had driven yourself or taken a subway.
COURTESY advanced transportation systems
This idea—known most popularly as personal rapid transit (PRT)—may sound far-fetched, but it is quickly becoming a reality in more than one municipality around the world. London’s Heathrow Airport will begin operating a PRT system known as ULTra as soon as next spring, connecting its business car park to Terminal 5, with more stations planned for the future. It will include 18 battery-powered cars running on solid rubber wheels along a U-shaped concrete guideway. “We didn’t set out to devise a PRT system,” said Martin Lowson of Advanced Transport Systems, the designer of ULTra. “We set out to design the best possible transport for the 21st century. When you ask what do people want from transit, everyone comes to the same conclusion: They want it now, they want to go where they want to go without stopping, and they want it to be sustainable.”
On a more ambitious scale, Foster + Partners is developing a PRT system as the primary mode of transportation for its Masdar project—a carbon-neutral city of 70,000 currently under construction outside of Abu Dhabi. The firm has placed the podcars on terra firma and moved all pedestrian spaces up on a raised deck. It has also done away with the guideway. Instead, the vehicles will follow sensors embedded in the road. “We started initially looking at track systems, then moved onto the sensor-driven systems,” explained Gerard Evenden of Foster + Partners. “By taking the vehicle off the track, you increase maneuverability and the flexibility of the system.”
PRT systems are also in the works for existing cities. This year the Swedish government announced plans to install systems in four of its cities: Stockholm, Södertälje, Umeå, and Uppsala; and South Korea announced similar plans for Suncheon. On the home front in California, the city of San Jose issued an RFP in August seeking consultants to help it develop PRT around its airport. Officials in Ithaca, NY, and Mountainview and Santa Cruz, CA, have also expressed interest in the modality. And just to prove that it’s not exclusively a pipe dream, a 2007 report issued by New Jersey found that PRT had the potential to “address certain transportation needs in a cost-effective, environmentally-responsible, traveler-responsive manner.”
On paper, it’s easy to see the allure of PRT. For one, it offers some of the benefits of the automobile—on-demand, nonstop travel to your destination—while at the same time soaring above traffic on dedicated guideways, like a monorail. Unlike monorail or light rail, however, which travel in corridors, the system can be laid out in a grid pattern extending in multiple directions to better service an urban area. The small vehicles are cheaper than large train cars and thus their guideways can be built lighter and at less cost. The smaller vehicles also offer the benefit of easier braking, which drastically reduces the headway necessary between cars, allowing them to run closer together. And the system is significantly greener than automobiles or conventional rail: The lightweight vehicles require little energy to move, their nonstop trajectory avoids using the energy wasted in stopping and starting at red lights or multiple stations, and they emit no pollutants at the point of usage.
Like many ideas that sound fresh or even futuristic today, PRT has been around for a long time. Several transit-oriented thinkers in the United States came up with the idea more or less simultaneously in the 1950s, but the system didn’t pick up steam until the ‘60s, when a report by the Department of Housing and Urban Development (HUD) entitled Tomorrow’s Transportation posited that current modes of transit would not be able to remedy the growing congestion in American cities and strongly endorsed PRT as the answer in 1966. The report sparked a rash of research and development in the ‘70s. PRT systems were drawn up for several cities—including Los Angeles, Houston, Boston, and Tucson—and a number of vehicle and guideway designs were constructed in test facilities.
brian m. powell
The only such system to ever be implemented in an urban setting was a federally funded, quasi-PRT system designed to connect the three disparate campuses of the University of West Virginia in Morgantown. While it had most of the features of a true PRT system—vehicles running direct from origin to select destination on a dedicated guideway, with no intermediary stops—the cars were quite large, capable of moving up to 21 people each. Unfortunately, planners rushed the project to an October 1972 completion date so that President Nixon could ride it at the system’s inaugural ceremony. While the world was watching, the system failed, and dealt a deadly blow to PRT. After that, the federal government wouldn’t go near the pods. Engineers later ironed out the kinks, though, and the Morgantown PRT has been operating efficiently ever since.
The HUD report stimulated the development of PRT systems in other countries as well, including Japan, France, and what was then West Germany. The West German system, known as Cabintaxi, was the most thoroughly tested of any PRT system. Designed as a transit option for the city of Hamburg, it featured cars running both atop and suspended below a box girder, allowing two-way traffic on a single guideway. Cabintaxi was ready for deployment by 1980, when a recession hit and the West German government withdrew funding.
The only other PRT system to come this close to implementation was TAXI2000, originally developed at the University of Minnesota by Dr. J. Edward Anderson. In the early 1990s, the Raytheon Company—a defense contractor—purchased the system in order to win a contract from the Northeastern Illinois Regional Transportation Authority to develop a demonstration PRT system for Rosemont, Illinois. Rather than build on Dr. Anderson’s designs, however, Raytheon started from scratch, putting the project in the hands of its radar engineers. As a result, the guideway grew three times as wide, the cars four times as heavy, and the system so inordinately expensive that the project was shelved.
But the failure of PRT to take hold can’t be blamed entirely on economic doldrums and engineering snafus. The system itself presents major concerns that have given city planners reason to pause. As a new modality, it has no record of success to hearten those about to invest millions of dollars in implementation. There is also no hard data indicating that people will feel comfortable in a driverless pod. And the elevated guideway would change the face of any city perhaps more than its citizens would accept. Recent advances in computing technology, however, have made automatic control much more reliable than it was in the ‘70s, and driverless trains in Europe are now racking up good marks for safety. “It’s not the technology that’s the problem. It’s all the hoops you have to run through to get acceptance,” said Jerry Schneider, a PRT advocate and member of the Advanced Transit Association. “What we need is a cowboy like Ted Turner who can afford to lose the money if it doesn’t work out.”