Automatic Train Protection (United Kingdom)

Automatic Train Protection was a method of beacon based railway cab signalling developed by British Rail. The system never progressed beyond the pilot schemes installed on the Great Western Main Line between London Paddington and Bristol, and the Chiltern Main Line from London Marylebone to High Wycombe and Aylesbury.

This article is about British Rail's implementation of ATP. For generic train protection systems, see Automatic train protection.

History

During the 1980s, an increase in trains passing signals at danger caused British Rail (BR) to develop a more comprehensive system than the existing Automatic Warning System (AWS). In 1988, a three-year program was launched to develop a system available to be implemented by 1992. Unlike the existing AWS system, which only advised the driver, leaving room for human error, Automatic Train Protection (ATP) would be able to take control of the train, ensuring it was driven according to the conditions (Gourvish 2002, pp. 355–356).

The two pilot schemes for the project were London Paddington to Bristol, and London Marylebone to High Wycombe and Aylesbury (Nguyen 2012). As a pilot scheme, the two systems were slightly different, with the Western scheme using ACEC equipment, and Chiltern using GEC General Signal (Gourvish 2002, p. 356).

There were plans to expand the system more widely, with BR stating that ATP would be installed on "a large percentage of its network" (Hamer 1995). Railtrack, who took over the management of rail infrastructure in 1994, later committed only to completion of the two pilot schemes, adaptation for new high speed lines, and to search for a cheaper alternative for the rest of the network (Gourvish 2002, p. 358).

It was later decided that TPWS would be rolled out instead of ATP (Watts 1997). This system automatically stops trains that pass red signals or speed restrictions at too high a speed, but does not monitor speed constantly, hence only mitigating SPADs, rather than preventing them (RSSB 2015, p. 10).

The total cost of ATP was estimated to be £750 million, equivalent to £1.131 billion in 2020 (Hamer 1995). In 1994 British Rail and Railtrack estimated that this would come to £14 million (£22 million today) per life saved, compared to the £4 million per life they considered good value for money (Hamer 1995). A Health and Safety Commission report later estimated a full installation of ATP would cost £11 million per life saved, or £5 million if only installed at high risk locations, figures Railtrack agreed with (Hamer 1995).

Function

The aim of ATP was to prevent trains from both exceeding speed restrictions, and from passing signals at danger (Nguyen 2012, p. 3). The system was beacon based, with information transmitted to the train at fixed beacons. The on board computer takes track and signal information from the beacons, and calculates the maximum speed of the train (Network Rail 2019, p. 24). When the maximum permitted speed decreases, such as when approaching a signal at danger, three braking curves are calculated: the indication curve, which is the ideal deceleration to the new limit; the warning curve, 3 miles per hour (4.8 km/h) above the indication curve, which causes a warning to the driver; and the intervention curve, 6 miles per hour (9.7 km/h) above the indication curve. At this point, the train will apply the brakes automatically (Nguyen 2012, p. 6).

References
  • Burrage, K.W. (1990). "Automatic Train Protection on British Rail: Present Plans and Future Possibilities" (PDF). Transportation Research Record. 1314: 10–14. Retrieved 8 March 2020.CS1 maint: ref=harv (link)
  • Gourvish, Terry (2002). British Rail 1974–97: From Integration to Privatisation. Oxford: Oxford University Press. ISBN 0-19-925005-7.CS1 maint: ref=harv (link)
  • Hamer, Mick (15 July 1995). "Safety signals set at danger". New Scientist (1986). Archived from the original on 8 March 2020. Retrieved 8 March 2020.CS1 maint: ref=harv (link)
  • Watts, John (11 March 1997). "Automatic Train Protector System". Parliamentary Debates (Hansard). 292. House of Commons. col. 143–144.CS1 maint: ref=harv (link)
  • Network Rail (21 June 2019). "Western Route Train Protection 0 to 12mp – Railway Safety Regulations 1999 Exemption Application Report" (PDF). Archived (PDF) from the original on 8 March 2020. Retrieved 8 March 2020.CS1 maint: ref=harv (link)
  • Nguyen, Hoang Nga (February 2012). "The BR ATP System" (PDF). Department of Computer Science, Swansea University. Archived (PDF) from the original on 8 March 2020. Retrieved 8 March 2020.CS1 maint: ref=harv (link)
  • RSSB (December 2015). "AWS and TPWS Handbook: RS/522 Issue 3 December 2015" (PDF). Archived (PDF) from the original on 8 March 2020. Retrieved 8 March 2020.CS1 maint: ref=harv (link)
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