The future of sustainable motorized transportation may resemble a driverless fully-enclosed golf-cart zipping 16 feet above the streets of North America's cities. Known by lots of names -- Skyweb Express, Taxi 2000, MicroRail, Higherway, and Skycab -- personal rapid transit (PRT) is a system for moving people in a way similar to how networked computers move bits of information around the Internet. PRT developers envision a system that combines the automobile's direct destination-to-destination convenience and privacy with public transit's capacity to reduce pollution, unclog traffic, and serve low-income communities.
The PRT idea has been around for decades, but now modern computer power is bringing it closer to reality. One prototype being demonstrated in suburban Minneapolis by the Taxi 2000 company features Jetsons-looking PRT cars that travel on narrow elevated 'guideways.' If a full system was built, the guideways would criss-cross a metropolitan area giving commuters a direct route to their destination. Though some cars are designed to hold as many as six people, PRT at heart is a private form of transit. A rider finds a station, selects a destination, and enters a car, leaving it to the computers to weigh the options and determine the best path. Route maps and schedule tables are unnecessary; the entire operation is designed around individual demand. Proponents say there will be no traffic jams, no gridlock, and no accidents because merging to and exiting to and from off-line stations will all be controlled automatically.
Because the cars are simple and lightweight, the guideways can be small and cheap and installed with minimal disruption. According to J. Edward Anderson, CEO of Taxi 2000, guideway systems can be built for $10 million per mile, an exceptionally low cost when compared with highways ($20 million) and light rail ($70 million). (A University of Washington study has estimated an even lower price tag for a metropolitan PRT system-about $5.5 million per mile.) Supporters note that PRT's lower cost per mile allows it to better serve spread-out communities. The higher cost of conventional rail means that subways and light rail serve only narrow corridors while PRT can fan out through a region.
PRT does have its critics, including those who question its basic feasibility and voice concerns about safety at stations and the aesthetic impact of building overhead guideways throughout a city.
PRT supporters respond that in a current design, the elevated PRT guideways are three feet square and can be built on streets and alleys and even through buildings. As a result, the system eats up less real estate than our current automobile infrastructure, which now accounts for more than half the land in many city centers. It's predicted that a single narrow PRT guideway could carry roughly the same capacity as a four-lane highway.
For more information on personal rapid transit, contact Citizens for Personal Rapid Transit (www.cprt.org).
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