ready when you are?

A professor in England thinks he has a solution to commuting woes: a personal rapid transit system.

It's a typical weekday morning and you're crawling along in heavy traffic, bumper to bumper on the freeway, right next to several hundred of your fellow commuters. While you're waiting, imagine what this traffic jam really represents: thousands of people stuck where they don't want to be, simply because they need to get from home to an office, school, or store.

There has to be a quicker, easier way to get people from Point A to Point B.

Creating that new transportation method is the goal of Martin Lowson and his students at the University of Bristol in England. They've designed a system they call ULTra (short for "urban light transport") that tries to be the "perfect" transit system: It's there when you need it and it takes you directly to the station of your choice.

Advanced Transport Systems Ltd., the University of Bristol spin-off company commercializing the ULTra system, has completed trials of a prototype on a test track in Cardiff, Wales. Once the funding comes through, a small circulator could be running there in a couple of years. But is ULTra ready for the real world? And is the real world ready for ULTra?

Fifty years ago, the solution to moving people quickly and efficiently was the very freeway that now doubles as a parking lot. People lived in low population-density suburbs, drove into the city center, and parked their cars in large lots near where they worked and shopped. There was traffic, but it was manageable.

But the freeways threading past farms and fields attracted developers who wanted to bring shopping closer to the motorized suburbanites. Enclosed malls, generally located along metropolitan beltways and surrounded by acres of blacktop, became new traffic magnets. Suburban office parks, following the same plan, created more suburb-to-suburb travel. By the 1970s, the metropolitan freeway systems designed in the 1940s and 1950s were straining to accommodate the new and unexpected travel patterns.

The resulting congestion has become, in the view of some planners, a cancer on the transportation system. Even building new highways—or expanding the capacity of the ones already built—seems to be just a Band-Aid solution.

If automobiles are becoming unmanageable in some areas, is public transportation the solution? Perhaps, but the public transportation system, robust and comprehensive in the early 20th century, has largely dissolved. In smaller metropolitan areas, buses are hard to come by; in larger ones, rails are designed to carry people into the job-losing city centers. Malls and office parks are poorly served by mass transit, and suburb-to-suburb commutes are almost impossible without a car.

Back in 1995, Martin Lowson, a professor of aerospace engineering at the University of Bristol, confronted a group of recent graduates with this very problem. "We asked ourselves what would be the ideal form of urban transport in the 21st century," Lowson said.

The team proceeded to outline certain desirable qualities for the proposed system. "What do people want? They want something that is available when they want it. They want to go where they want to go, nonstop. They want their transportation mechanism to be energy efficient, and have zero emissions."

Dealing with those constraints, the group worked up a design that disregarded many of the conventions of public transportation. There would be no drivers and no schedule. Vehicles would sit in the station, waiting to be ridden, rather than force riders to wait at the station for their rides to show up. Passengers could choose whom they rode with—or they could ride alone.

As proposed, the system would run on flat steel-and-concrete tracks elevated over streets or on the surface alongside highway or railroad rights-of-way. Automated four-seat cars would run on the guideway (the ULTra's track), picking up passengers from stations on sidings off the main line and traveling nonstop to a destination, another off-line station. The vehicles would run at about 25 miles per hour, which seems slow, but since they run nonstop, the savings in time promise to be substantial, especially in congested city centers. (More details of the system can be found at www.atsltd.co.uk.)

Pod People

"Once our system emerged," Lowson said, "we looked around to see if there were other similar systems that had any important aspects we had missed. And we saw that there were parallel concepts around."

Personal rapid transit, or PRT, is a concept that dates back more than 30 years. But it is hardly surprising that Lowson hadn't heard of the idea before kicking off his class project. Although PRT has a cadre of ardent advocates, the concept has never been implemented on a full-scale basis.

A compendium of PRT schemes catalogued on Innovative Transit Technologies, a Web site dedicated to alternative transportation ideas, lists more than two dozen personal rapid transit proposals. Almost all of those, however, are scarcely more than slick drawings and sketchy scenarios. Some invoke magnetic levitation to enable speeds of more than 200 mph; others propose running pods through evacuated tubes. They all seem to address some, if not all, of the ideals that Lowson and his students identified.

One scheme that has progressed beyond the prospectus stage is proposed by Taxi 2000, a Minneapolis-based group headed by University of Minnesota professor Edward Anderson. Anderson has been studying PRT technology for decades. He designed some advances in computer control technology that enable the vehicles to travel autonomously from station to station.

ULTra vehicles can accommodate four adults. The system has been studied on a test track near Cardiff, Wales, and is now ready to be deployed.

In the early 1990s, Anderson's group licensed Raytheon Corp. of Waltham, Mass., to develop its patents into a full-fledged transportation system. The Chicago suburb of Rosemont had expressed interest in a system that would link a commuter rail system with hotels and the McCormick Place convention center in Chicago. Raytheon saw the opportunity for developing a new product line. The company built a full-scale test loop near its Massachusetts headquarters to shake down the system, which was renamed PRT 2000.

But after eight years and $40 million, the system proved to be unworkable. The company gave up on personal rapid transit, although groups in Korea and England (unrelated to the ULTra group) have tried to revive the Raytheon system. Edmund Rydell, an engineer who has been a long-time director of Taxi 2000, says the whole enterprise suffered from bloat—the cars became too heavy, which increased the weight of the tracks, which increased the cost of the entire system.

"With their experience as a huge defense contractor, they were ill-equipped to tackle this market," Rydell said of Raytheon. "They didn't have the kind of analysis they needed, and instead of using the patents they paid for, they reinvented the whole system."

Taxi 2000 now has a prototype called SkyWeb up and running on a 60-foot length of guideway, and is raising money to build a test track of its own. But after disappointments with Raytheon's PRT 2000 and with work that Taxi 2000 has performed in the Cincinnati and Seattle areas, Rydell thinks the way forward for PRT may be on private property: office parks and resorts, for instance. There, the pressures to overbuild to accommodate every contingency and constituency would be lessened, enabling the system to be simple and light enough to be profitable, he said.

"Cities are fraught with bureaucratic problems," Rydell said, "and airports, though they have tremendous potential, are almost as bad. But on private property and with private money, we can avoid all the red tape."

Keep It Simple . . . And Small

In Cardiff, a half-mile test track for ULTra has been up and running since 2001. Lowson and his team have taken to heart the lessons from Raytheon's failure. "Raytheon didn't pay enough attention to the infrastructure," Lowson said. "It got seriously oversize and overweight and therefore over cost. We've spent a lot of time looking at optimizing the infrastructure." For example, the depth of the steel guideway is only 18 inches, which saves on material both in the guideway itself and in the structures that support it.

"The span-width ratio exceeds the normal rule of thumb, but we can exceed them because our loads are very different," Lowson said. "It's not a footbridge, and it wouldn't work as a footbridge because it's too thin. But it works as a PRT guideway."

And unlike Raytheon, which developed all the technology for its system from scratch, Lowson's team concentrated on finding off-the-shelf parts to build ULTra. Lowson's group built the vehicles from automotive industry parts, which enabled them to piggyback on decades of research. Consequently, Lowson says that ULTra has greater reliability and lower costs than other transit systems.

As a result, Lowson says he can deliver ULTra at a cost of between $8 million and $12 million a mile, far cheaper than conventional light rail systems. And in comparison to relatively inexpensive solutions such as diesel buses, ULTra can theoretically carry far more people per hour. Based on rider studies conducted in Cardiff and on estimates of the capacity of the line, the system could deliver about 2,000 people each hour among a dozen stations.

ULTra vehicles travel under computer control.

"We've met all our contracts to date on both time and cost," Lowson said, "which suggests to us that our cost estimates are realistic." Work on building a pilot system in Cardiff has been delayed because of a holdup in funding the system from the National Assembly of Wales. Until that application gets full funding, Lowson has been talking to airports about building a system to ferry passengers from parking lots to terminals. One study showed that ULTra could run 40 percent cheaper than conventional shuttle buses, according to Lowson.

Still, the jury is out on whether PRT will really work in practice. More than one transportation researcher has dismissed the technology as an application for a future that will never come. Vukan Vachic, a professor of transportation engineering at the University of Pennsylvania in Philadelphia, says that PRTs don't have a natural niche: The capacity is too small to handle the morning rush into a city center, and the cost per mile is too high to adequately service a low-density suburban setting.

"You cannot handle large numbers of passengers in small vehicles," Vachic said. "Large office buildings don't have 30 shafts of two- or four-person elevators because they can't handle the capacity.
"With PRTs, you're combining the expensive infrastructure that rapid transit needs with the inefficiency of the automobile," Vachic said. "It just doesn't work together."

Indeed, in spite of all the imagined advantages in quality of service, it seems difficult to imagine how a PRT system could handle the volume of a subway line. In New York City, for example, rush hour subway trains carry 1,000 to 2,000 riders each trip, and many lines run up to 20 trains an hour. Even with very short headways between vehicles, it would take a dozen PRT lines to handle the ridership of one subway line.

But Lowson waves off such objections. The system is not designed to replace subways, but to provide an alternative to the automobile for many everyday trips.

"In the U.K., we're finding that people who don't have access to a car—poor people, people with disabilities, and the like—are particularly attracted to our system," Lowson said. "They often have to get around in taxis, and compared to the price of a taxi, our system—which we project to price at less than two dollars a ride—would be a bargain."

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