Technology News - December 15, 2004

Taking the mass out of transit

Even if public transit systems use state-of-the-art, less-polluting trains, trolleys, light rails, and buses, the people-moving principles hark back to Victorian times. Passengers wait at designated locations at specific times, follow a universal route in a large group, and may have to transfer within the system to get where they need to go. But some visionary transportation engineers are convinced that the time is right for expanding the concept of public transport to include something a bit more personal.

Credit: Taxi 2000 Will PRT work this time? SkyWeb Express is ready to find out.

Enter personal rapid transit. PRT promises environmental benefits and the privacy and point-A-to-point-B convenience of a car without the hassle of actually owning one or even sitting in traffic. Simply arrive at an aboveground station, pay a fare, hop into a waiting aerodynamic, pod-like vehicle, punch in your destination, and go. No schedules, stopping along the way, or riding with strangers. The driverless vehicles are programmed to take the shortest route in a network of loops. PRT vehicles seat 2–4 people and leave just enough room for luggage, a baby carriage, or a wheelchair.

PRT may sound familiar because the concept has been tested but never put into service. Developers say that proposals in the 1970s were too advanced for the available technology. The closest thing to PRT is operating at West Virginia University in Morgantown, but the vehicles each carry too many passengers for this to be considered a true PRT system. However, advances in technology since the 1970s have created renewed interest in PRT around the globe. Approximately 15 concepts are now in various stages of development, and 2 have reached the prototype stage.

Martin Lowson of Advanced Transport Systems in Bristol, U.K., developed Urban Light Transport (ULTra). The system is now certified to carry passengers, following last summer’s successful tests, which evaluated the safety of the 800-kilogram vehicles traveling about 25 miles per hour on a 1-kilometer prototype track in the Cardiff Bay area in Wales. These futuristic vehicles are 1.6 meters high and 1.45 meters wide and made of a composite material over a steel frame, and are based on automotive technology: rechargeable batteries power the vehicle, which has 4 rubber tires and travels on its own “road”, like a curb-guided bus. This guideway can be elevated over roads or sidewalks.

Lowson applied for approval to build an ULTra system at Heathrow Airport in London at the end of 2004. The British Airport Authority has several projects to reduce pollution and “is principally interested [in ULTra] for environmental gain,” he adds. If accepted, the system could be shuttling passengers between parking lots and terminals by 2006.

A PRT system in the United States has many similar features. J. Edward Anderson, a PRT pioneer, created a company called Taxi 2000 to research, develop, and market his system, SkyWeb Express. A test track is under development in Minnesota and is expected to be ready for testing in two years. Vehicles in this PRT system have similar dimensions to those in ULTra but weigh only 533 kilograms. The body of the vehicle is also a made of a composite material but is placed over an aluminum frame. These vehicles are propelled by two linear induction motors, have pneumatic and polyurethane wheels for stabilization, and run on an electrified steel guideway. “As of 2–3 years ago, there was still an attitude [in the United States] that we could build our way out of congestion, if we just added enough freeway lanes or if we just put in a train,” says Jeral Poskey, director of applications for Taxi 2000. But he thinks the attitude is changing. “We can’t build enough roads or trains by themselves to eliminate congestion. We’ve got to add something new.”

Transit officials debate statistics that show that newer cars and current rail systems have the same energy efficiency. Like many heavy- or light-rail systems, PRT is electric, but the vehicles are lighter so less energy is used. Moreover, PRT systems should appeal to people who avoid “that crowded public transit” and should get them out of their cars.

Less energy means lower operating costs. ULTra and SkyWeb Express guideways are fairly small (1.5 feet high by 6 feet wide and 3 feet high by 3 feet wide, respectively, not including posts). Lowson quantifies PRT construction at 2–3 times less expensive per mile than light rail. Other estimates show that the per-mile cost of PRT with elevated construction is lower than building something of similar stature, like a pedestrian overpass.

If the economics are good, will the public sector embrace PRT? The United States is tentative overall, according to PRT developers, but the EU is supporting PRT development. Travel patterns are changing, says Eric Ponthieu, head of the sector for Urban Sustainability and Cultural Heritage for the European Commission (EC) in Brussels. “Thirty years ago, the main motive for traveling was commuting, [but] today shopping and leisure trips constitute 70% of all trips in Europe.” He adds that these patterns pose real difficulties for public transport as it exists today. The EU needs flexible transportation options, Ponthieu explains. “There is no way to promote any unique solution for Europe,” he says. Member states have different geography, available resources, and preferences for fuels, he explains. “It is the role of EU research to contribute to the development of a range of different sustainable alternatives, including PRT.” Ponthieu cautions that the EC sees PRT “as a positive development which will have to be pursued and carefully assessed at regular intervals in order to compare the merits of PRTs with other alternatives.”

Citizen critics, on the other hand, worry that a PRT system could look ugly, lack handicap access to elevated stations, and lead to antisocial behavior by encouraging people to ride alone. Engineers take issue with the system’s logistics. “The whole concept of PRT really doesn’t have enough capacity in high-density areas, and it doesn’t have economic justification in low-density areas,” says Vukan Vuchic, a transportation systems engineering professor at the University of Pennsylvania. He is even skeptical of the airport application. He agrees that electricity would be better for the environment but asks, “Aren’t we trying to put auto drivers into multioccupancy vehicles to reduce the cost, the congestion, the air pollution, and to make the whole transportation system much more economical?”

Lowson and Poskey acknowledge that the current forms of their systems could not replace very high capacity systems such as London’s Underground or New York City’s subway. Yet, PRT can “complement what is already there, serving as a feeder and distribution service to big rail and bus lines,” says Poskey. —RACHEL PETKEWICH