London Overground Class 317 EMU
- London Liverpool Street – Chingford
- London Liverpool Street – Cheshunt
- London Liverpool Street – Enfield Town
- Romford – Upminster
Introduced: 1981 Number in Service: 14 Number of Carriages: 4 Max Speed: 100mph
The Class 317 electric multiple units were built by British Rail Engineering Limited’s York works from 1981 to 1982.
The units were originally built to operate services on the newly electrified London St Pancras to Bedford route where they replaced the elderly and unreliable diesel multiple units, however, they did not enter service immediately due to an industrial dispute with the unions over Driver only operation, meaning the diesel units continued in operation until finally being replaced in mid-1983.
In 2000, nine Class 317 units were selected to be refurbished for the dedicated Stansted Express service from London Liverpool Street. These units continued in service until the arrival of new Class 379 units on Stansted Express services in 2011.
When Abellio took over the East Anglia franchise on 5 February 2012, the Class 317/7s were deemed too expensive to lease and surplus to requirements, and so they entered storage.
On 31 May 2015, London Overground took over the operation of Lea Valley Line services from Abellio and promptly took the 317/7 units out of storage and they are now used alongside 6 Class 317/8 units exclusively on Lea Valley services and the Romford – Upminster line. London Overground announced in July 2015 that the Class 317 units it leases will be replaced in 2018 by 45 new Bombardier Aventra Class 710 EMUs, similar to the Class 345s that will be used by Crossrail.