Ultra (a term formed from the first letters of the words in the phrase "urban light transit") is a personal rapid transit podcar system developed by the British engineering company Ultra Global PRT (formerly Advanced Transport Systems). The only publicly operating Ultra pod system opened at Heathrow Airport in London in May 2011 and is referred to as the Heathrow pod system. It consists of 21 vehicles operating on a 3.9-kilometre (2.4 mi) route connecting Terminal 5 to its business passenger car park, just north of the airport. To reduce construction costs, Ultra largely uses off-the-shelf technologies, such as rubber tyres running on an open guideway. The approach has resulted in a system that Ultra believes to be economical: the company reports that the total cost (vehicles, infrastructure, and control systems) is between £3 million and £5 million per kilometre (0.62 miles) of guideway. By contrast, the Heathrow deployment cost £30 million for 3.8 kilometres (2.4 mi) of guideway.
Inception The system was originally designed by Martin Lowson and his design team; Lowson had put £10 million into the project. He formed Advanced Transport Systems (ATS) in Cardiff to develop the system, and the site was later the location of its test track. Ultra has twice been awarded funding from the UK National Endowment for Science, Technology and the Arts (NESTA). Much of the original research on Ultra was done by the Aerospace Engineering department at the University of Bristol in the 1990s. The company renamed itself "Ultra PRT Limited", because of its primary business, and moved its corporate headquarters to Bristol.
Background
Past PRT designs Personal rapid transit was originally developed in the 1950s as a response to the need to move commuters in areas with densities too low to pay for the construction of a conventional metro system. Using automated guidance allowed headways to be shortened, even to a few seconds. That increases the route capacity, allowing the vehicles to become much smaller but still carry the same passenger load in a given time. Smaller vehicles in turn would require simpler "tracks" and smaller stations, which lowered capital costs. Smaller towns and cities that could never hope to fund a conventional mass transit system could afford PRT, and the concept generated intense interest. Numerous PRT systems were designed in the late 1960s and early 1970s, many as a result of the publication of the highly-influential HUD reports. In general, the systems intended to use small four-to-six-passenger vehicles, but most evolved to larger designs over time (see Alden staRRcar). As they did so, vehicles and tracks grew heavier, capital costs rose, and interest dropped. In the end, only one production PRT system was built, the Morgantown, W.Va PRT in 1975, a government-funded demonstration system to prove the concept. Originally derided as a white elephant, the Morgantown system has since proven itself both reliable and relatively low cost.
Ultra In the time since the Morgantown system was installed in 1975, general technological improvements have led to a number of ways to lower the cost of a PRT system. One of the simplest but most profound way was the development of more efficient, reliable and quick-charging battery systems. Older PRT systems used electricity fed from track-side conductors like a conventional metro, but they can be eliminated in favour of batteries that quickly charge up at stations or small charging strips along the route. Another change is the moving of the guidance logic from centralised computers to on-board systems of dramatically improved performance, allowing the vehicles to steer and switch themselves between routes on their own. That eliminates the need for a track-mounted guiderail able to steer the vehicle (see, for instance, the Ford ACT). Together, the changes mean the vehicle no longer needs strong mechanical contact with the guideway, which can be dramatically reduced in complexity. In the case of Ultra, the guideway can consist of as little as two parallel rows of concrete barriers, similar to the bumpers found in a car park. The vehicle uses them for fine guidance only; it is able to steer itself around curves by following the barriers passively. No "switching" is required on the track, as the vehicles can make their own turns between routes based on an internal map. Since the vehicles are battery-powered, there is no need for electrification along the track: the vehicles recharge when they are parked at the stations. As a result, the trackway is similar in complexity to a conventional road surface, a light-duty one as the vehicles will not vary in weight to the extent of a tractor-trailer. Even the stations are greatly simplified; in the case of ground-level tracks, the lack of any substantial infrastructure means that the vehicles can stop at any kerb. Stations at Heathrow resemble a car park with diagonal slots, with a rain shield similar to the awnings at a petrol station. As part of the development of the first commercial system at Heathrow Airport, in 2005 the owner of the airport, BAA Airports Ltd, purchased 25% of the company. Following its successful launch, there are now plans to extend it to the rest of the airport and even to the nearest town of Staines-upon-Thames, which is home to many of the airport's staff.
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