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by Daniel Thomas
With a 1.7-mile tunnel, maintenance yard, and stations under construction, Minneapolis' Light Rail Transit (LRT) system is on full steam ahead. The $675 million project came through a mountain of controversy, much of it from public transit experts themselves. Though many other transit systems were proposed, they were given little chance.
One of the main alternatives proposed was Taxi 2000, a leading Personal Rapid Transit (PRT) design for small, automated, electric cars on a elevated guideway. PRT is an attempt to improve transit speed, efficiency and comfort while allowing the personal freedom that binds commuters to their cars.
Entering an enclosed off-line PRT station, a passenger purchases a magnetically coded ticket. This ticket opens the door of the first waiting PRT car and allows a computer to plan the trip along the guideway network. The car proceeds without stops to the destination at a speed of up to 50 mph, following the shortest possible route. Sharing the three-person car allows a lower fare, although the wait for a car never exceeds three minutes.
The Taxi 2000 PRT system has its roots at the University of Minnesota, where a multi-disciplinary team of researchers started developing it in 1982. Since then, Mechanical Engineering Professor Emeritus Edward Anderson has continued development with the Taxi 2000 Corporation.
Defense contractor Raytheon Corporation bought the Taxi 2000 rights in 1993. They spent over $40 million developing it, modifying the design, and winning a transit project contract for northern Illinois. When the Chicago Regional Transportation Authority delayed their order, Raytheon discontinued development and rights were returned to Taxi 2000.
There are many other PRT designs being developed: some very similar to Taxi 2000 and some, such as the Danish Rapid Urban Flexible (RUF) PRT, quite different. RUF uses modified electric cars that run on roads or in driverless platoons on a monorail. Areas currently considering PRT include the Seattle-Tacoma International Airport region, Cincinnati, and Northern Kentucky. In the West Virginia University in Morgantown, a system similar to PRT has been in use since 1975.
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Characteristics of PRT
Recognizing the failure of conventional mass transit systems to lure commuters from their cars, PRT is a transit option that attempts to combine the privacy, comfort, and freedom of cars with the safety, predictable travel times, and low pollution of public transit.
PRT vehicles are designed to be relatively small, as Anderson found the vehicle cost per seat did not decrease as car size increased. Smaller vehicles allow not only for selection of traveling companions and the option of individual travel, but also for the vehicle to wait for the rider, not vice versa. In addition, smaller vehicles put less force on the guideway, allowing the track to be lighter and cheaper.
Stations can also be smaller, cheaper and more frequent. More frequent stations do not slow PRT traffic, because all deceleration and acceleration is done on a parallel station track. There is no need to transfer and the shortest route to the destination is chosen.
Automated control of vehicles allows them to travel safely with small headway, and thus allows a single PRT line to move as many people as three lanes of freeway. The uninterrupted trip not only increases trip speed, PRT vehicles also increase transit system efficiency. PRT avoids the loss of kinetic energy involved in the frequent stops of road traffic and trains. As a result, experts estimate PRT to be about six times as efficient as LRT. PRT cars require about 145 watt-hours of electric energy per vehicle-mile at 25 mph. This is approximately equivalent to a gasoline-powered car getting 70 to 90 miles per gallon. The efficiency of PRT cars is aided by light, streamlined vehicles and electric linear induction motor, which eliminates idling at stations.
The PRT Battle in the Twin Cities
In Minneapolis, where most of the Taxi 2000 development has occurred, PRT has received little attention, losing out to the conventional technologies of bus and LRT.
When an initial plan for a six-lane freeway connecting the airport to downtown Minneapolis along the congested Hiawatha corridor was rejected, largely due to opposition from communities along the route, a door was opened for alternative transit solutions.
Many suggestions, including PRT, were put forward. However, according to Nacho Diaz, Director of Transportation for the Metropolitan Council, the governing body that operates and plans Twin Cities transportation systems, light-rail was considered the only serious alternative from early in the process. With a strong LRT lobbying force effectively blocking consideration of other options, the city of Minneapolis went ahead with LRT plans and the groundbreaking ceremonies were held in January.
According to Anderson, the decision makers see PRT only as a "spoiler for getting light-rail." Anderson also blames over 30 years of strong lobbying and support for bringing back streetcars and potential LRT construction contracts for lack of interest in PRT. Despite the facts supporting PRT, he says many also have the idea that, "bringing back light-rail has got something to do with improving the environment."
"The fact is there are a lot of people who don't look at the facts," Anderson said, suggesting that many favor light-rail based on intuition. "Our governor is one of those, and he is all behind building more rail lines around the Twin Cities."
While he still sees a future for a PRT system that would connect downtown Minneapolis and feed the LRT line, Anderson says Taxi 2000 has the international market in mind.
New Horizons for PRT
The current focus of Taxi 2000 is raising money for a 2200-foot test track with three vehicles and one station, for which detailed plans have been made. This is an attempt to overcome the major obstacle to PRT acceptance: the lack of existing models.
The first phase of this test track would be a single prototype vehicle and 60-foot track, which together would cost less than $1 million. This is the length of prefabricated track modules that would allow quick installation at an estimated cost of about $7 million per mile.
Citizens for Personal Rapid Transit, a grassroots volunteer organization promoting PRT in Minneapolis, carries out its mission to educate politicians and the public about PRT. According to Anderson, there are now several state legislators who support PRT.
While disappointed that PRT has yet to be seriously considered by planners, supporters say it can become integrated with the current LRT development. Brian Finley, chairman of Citizens for Personal Rapid Transit, says PRT would now be most effective as an LRT feeder in Bloomington, with a line from the Mall of America along I-494 to Highway 100 and a link running up France Avenue to Southdale. If practically accepted, with a line up and running, PRT may yet find its golden days.
FOR MORE INFORMATION:
www.taxi2000.com
www.cprt.org
