page_title: British Rail Class 317
section_title: Class 317/1
hierarchical_section_title: British Rail Class 317 / Description / Class 317/1
caption_attribution_description: 317340 calls at Welwyn Garden City, with a southbound service for London Kings Cross
context_page_description: The British Rail Class 317 is an alternating current electric multiple unit constructed by British Rail Engineering Limited in two batches, 48 sets being produced in 1981–82 and 24 sets in 1985–87. They were the first of several classes of British Rail EMU to be based on the all-steel Mark 3 bodyshell, departing from the "PEP"-aluminium design which had spawned the earlier Class 313 to Class 315, Class 507 and Class 508. The Mark 3 bodyshell was also the basis of Class 318, Class 455, and the diesel Class 150.
context_section_description: The first batch of 48 units, built in 1981-82, were classified as Class 317/1. Units were numbered in the range 317301-348, and had a maximum speed of 100 mph. 
  In the first batch, 3 of the 4 cars in each set were built at Holgate Road carriage works and the remaining car at Derby Litchurch Lane Works, whilst the bogies for all were manufactured at Derby Locomotive Works.
  Each unit consisted of four carriages; two outer driving 2nd class only vehicles, an intermediate trailer with both 1st and 2nd class, and a motor vehicle with 2nd class seating, roof mounted Stone Faiveley AMBR pantograph and four GEC G315BZ traction motors.
  The technical description of the formation of the units is DTSO(A)+MSO+TCO+DTSO(B). Individual carriages were numbered as follows:
  77000-77047 - DTSO(A)
  62661-62708 - MSO
  71577-71624 - TCO
  77048-77095 - DTSO(B)
  The units were built to operate services on the newly electrified London St Pancras to Bedford route and were due to replace the elderly (and unreliable) Class 127 diesel multiple units in October 1982. However, they did not enter service immediately due to an industrial dispute with the unions over driver-only operation, and the diesel units lingered on until finally being replaced in mid-1983. Units were delivered in the standard livery of BR blue/grey.
  In 1986, the route came under control of the Thameslink subsector of newly created Network SouthEast. From 1987, new dual-voltage Class 319 units were introduced on the route, allowing the creation of a new cross-London service, from Bedford to Brighton, via Farringdon and City Thameslink station. The Class 317 units were displaced to outer-suburban services on the WCML out of London Euston to Milton Keynes and Northampton. They replaced the slam-door Class 310 units, which subsequently transferred to the London, Tilbury and Southend railway.
  However, the use of Class 317 units out of Euston again proved to be short-lived. In 1989, the second batch of new Class 321 were introduced onto WCML services. The Class 317 units were again displaced, this time to the Great Northern and West Anglia routes out of London King's Cross and London Liverpool Street, where they joined the second batch units. Therefore, for the first time, the entire Class 317 fleet was operating in the same place.
caption: First Capital Connect Class 317 No. 317340 at Welwyn Garden City
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