Personal Rapid Transit - Overview

Overview

Most mass transit systems move people in groups over scheduled routes. This has inherent inefficiencies. For passengers, time is wasted by waiting for the next arrival, indirect routes to their destination, stopping for passengers with other destinations, and often confusing or inconsistent schedules. Slowing and accelerating large weights can undermine public transport's benefit to the environment while slowing other traffic. Personal rapid transit systems attempt to eliminate these wastes by moving small groups nonstop in automated vehicles on fixed tracks. Passengers can ideally board a pod immediately upon arriving at a station, and can — with a sufficiently extensive network of tracks — take relatively direct routes to their destination without stops.

Perhaps most importantly, PRT systems offer many traits similar to cars. For example, they offer privacy and the ability to choose one's own schedule. PRT may in fact allow for quicker transportation than cars during rush hour, since automated vehicles avoid unnecessary slowing. A PRT system can also transport freight.

The low weight of PRT's small vehicles allows smaller guideways and support structures than mass transit systems like light rail. The smaller structures translate into lower construction cost, smaller easements, and less visually obtrusive infrastructure.

As it stands, a city-wide deployment with many lines and closely spaced stations, as envisioned by proponents, has yet to be constructed. Past projects have failed because of financing, cost overruns, regulatory conflicts, political issues, misapplied technology, and flaws in design, engineering or review.

However, the theory remains active. For example, from 2002–2005, the EDICT project, sponsored by the European Union, conducted a study on the feasibility of PRT in four European cities. The study involved 12 research organizations, and concluded that PRT:

  • would provide future cities "a highly accessible, user-responsive, environmental friendly transport system which offers a sustainable and economic solution."
  • could "cover its operating costs, and provide a return which could pay for most, if not all, of its capital costs."
  • would provide "a level of service which is superior to that available from conventional public transport"
  • would be "well received by the public, both public transport and car users."

The report also concluded that, despite these advantages, public authorities will not commit to building PRT because of the risks associated with being the first public implementation.

Comparison of Personal Rapid Transit with existing transport systems
Similar to automobiles
  • Vehicles are small—typically two to six passengers
  • Vehicles are individually hired, like taxis, and shared only with the passengers of one's choosing
  • Vehicles travel along a network of guideways, much like a network of streets. Travel is point-to-point, with no intermediate stops or transfers
  • Potential for on-demand, around-the-clock availability
  • Stops are designed to be off the main guideway, allowing through traffic to bypass stations unimpeded
Similar to trams, buses, and monorails
  • A public amenity (although not necessarily publicly owned), shared by multiple users
  • Reduced local pollution (electric powered)
  • Passengers embark and disembark at discrete stations, analogous to bus stops or taxi stands
Similar to automated people movers
  • Fully automated, including vehicle control, routing, and collection of fares
  • Usually off-grade—typically elevated—reducing land usage and congestion
Distinct features
  • Vehicle movements may be coordinated, unlike the autonomous human control of automobiles and bikes
  • Small vehicle size allows infrastructure to be smaller than other transit modes
  • Automated vehicles can travel close together. Possibilities include dynamically combined "trains" of vehicles, separated by a few inches, to reduce drag and increase speed, energy efficiency and passenger density

The PRT acronym was introduced formally in 1978 by J. Edward Anderson. The Advanced Transit Association (ATRA), a group which advocates the use of technological solutions to transit problems, compiled a definition in 1988 that can be seen here.

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