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ULTra Personal Rapid Transit
An ULTra vehicle at the ATS test track in Cardiff, Wales

About ULTra

The ULTra Personal Rapid Transit (PRT) system, developed by Bristol-based Advanced Transport Systems Ltd, consists of small, lightweight, computer-driven electric vehicles running on slender, special-purpose guideways. The system is designed to offer numerous advantages over conventional road and rail public transit systems, including:

  • Low capital and operational costs
  • Flexible routing
  • 24-hour availability
  • On-demand service, with no transfers
  • Greater privacy
  • Zero on-site emissions
  • Extremely low overall energy use
  • Minimal visual and acoustic impacts

ULTra is not a replacement for buses or trains, but is intended to bring high-quality public transport into environments which buses or trains cannot easily access. This is expected to enhance the ridership and quality of all forms of public transit.

Example ULTra networkULTra Networks

Unlike mass transit, which requires linear routes with a limited number of intermediate stops, ULTra networks can be complex, multi-directional webs. The vehicles route themselves through the network, bypassing all intermediate stations until they reach their final destination. In this way, ULTra networks can create a higher service density than mass transit, without compromising the overall system speed or throughput.

ULTra networks are not intended for long-distance travel, however. Those roles are best fulfilled by rail or Bus Rapid Transit systems. ULTra networks work best as "local circulator" systems, and as "feeder" systems for longer-range transit services.

Vehicle InteriorULTra Vehicles

ULTra vehicles are rubber-tyred, battery-powered vehicles, capable of carrying 4 passengers and their luggage. They are fully accessible to prams and wheelchairs, and have sufficient room to carry 2 passengers and their bicycles. With a turning radius of only 5m (16 ft) and an empty weight of 820kg (1,800 lb), the vehicles can navigate complex routes with minimal supporting infrastructure. The vehicles are virtually silent and produce little or no external vibration; this allows the system to function in close proximity to both work and residential areas without disturbance.

View of the guideway from belowULTra Infrastructure

Lightweight and manoeuvrable vehicles allow for lightweight and highly flexible infrastructure. ULTra can operate below-grade (via cut-and-cover tunnelling), at-grade, or above-grade (elevated). Guideways and stations can also be sited inside buildings, because electric propulsion is silent and emission-free. Low dynamic loading means that the vehicles can run through conventional building structures with no need for additional reinforcement.

The ULTra guideway consists of any flat, drivable surface, 1.6m (5'-3") wide, with 25cm (10") kerbs that are used for optical navigation. The guideway is entirely passive, with no mechanical elements or power systems. This allows for tremendous flexibility in the design and visual appearance of both the guideway and stations.

Adapting the ULTra design to best suit different environments is already a subject of considerable interest. A good starting point is PRT - The Urban Challenge, by Jochen Rabe of Arup (presented by Tony Kerr at the PRT@LHR conference, in April 2009). Arup, which has been involved with the ULTra project since its beginning in 1995, has kindly made the presentation available for this competition.

Coming to Heathrow in 2009

This year the first public ULTra system — which is also the first commercial PRT system anywhere in the world — will open at London’s Heathrow Airport. The system comprises some 4 kilometers of track and will link one station in Terminal 5 to two remote stations in the Business car park. This simple application may later be expanded to include around 30 kilometers of track, 350 vehicles and 50 stations serving Terminals 1, 2, 3 and 5, linking them to office blocks and hotels in the vicinity of the airport.