Following the implementation of the London Underground
Public Private Partnership (PPP) in 2003, the
Metronet consortium became responsible for the infrastructure on the District, Circle, Hammersmith & City and Metropolitan lines. As part of the consortium,
Bombardier Transportation would design, build and maintain new trains for these lines. 190 trains would be built by Bombardier at
Derby Litchurch Lane Works – 40 trains for the Circle and Hammersmith & City lines, 78 trains for the District line, and 72 trains for the Metropolitan line. The first train was planned to enter service on the Metropolitan line by 2009, with all trains in service by 2015. London Underground also announced that 40 additional cars had been ordered from Metronet/Bombardier at a cost of £105 million. This would allow for a seventh carriage on Circle and Hammersmith & City line trains, unifying the fleet with the District line trains. Following negotiations with Bombardier to allow for continued delivery of
2009 Stock and S Stock trains, TfL took ownership of Metronet in May 2008. A mockup of the train was shown off to the public in September 2008.
Entry into service From March 2009, trains were tested prior to delivery at
Old Dalby Test Track in
Leicestershire, preventing the need for weekend or evening closures of lines in London to test trains. The first train was delivered to London Underground in October 2009. In 2015, TfL ordered an additional S8 train as part of the
Croxley Rail Link at a cost of £15.5million, taking the total ordered to 192. The final set was delivered 10 November 2016. The extension to the Metropolitan line was cancelled in 2017.
Metropolitan line S8 Stock was initially tested overnight between and via the Watford North Curve from 9 November 2009. Driver training began in early January 2010, and the first train entered revenue service on 31 July 2010, shuttling between Wembley Park and Watford. In November 2012, it was reported that 37 of the new trains would be sent back to Bombardier for urgent modification at Bombardier's cost, and that drivers were unhappy with their cabs.
Hammersmith & City line in July 2013 The first trains entered service on 6 July 2012, from Hammersmith to Moorgate. S7 trains are longer than the C69 and C77 trains they replaced (seven cars and long instead of six cars and long), so some station platforms had to be lengthened to allow for S7 operations. For stations where this has proved physically impossible, such as , the trains use their selective-door-opening capability whereby the doors at the end of the train will not open. and completely replaced the C Stock trains on the line by 11 February 2014.
District line train next to an S7 Stock train at
Ealing Broadway station on 21 April 2017. The District line was the last line to be fully served by the S7 Stock, due to its existing D78 Stock being newer than other trains that the S7 Stock was ordered to replace, as well as its most recent refurbishment in 2005. The first S7 Stock train entered passenger service on the line between Olympia and West Ham on 2 September 2013. On 6 February 2014, the S7 Stock started running between Wimbledon and Edgware Road. The S7 Stock started services to Ealing Broadway on 13 June 2014, and on 17 June saw the start of commercial service to Richmond. On 16 January 2015, the S7 Stock began running to Upminster. Withdrawal of the D78 Stock began on 19 January. In November 2016, the last of 192 S stock trains were completed by Bombardier and handed over to London Underground. The D78 Stock was completely replaced by the S7 with the withdrawal of the final unit from service on 21 April 2017. The S7 Stock received the
Class 499/5 designation on the
TOPS system in order to operate on the District line between
Gunnersbury and
Richmond, and between
East Putney and
Wimbledon, as these track sections are owned by
Network Rail.
Automatic operation From 2016, the
Four Lines Modernisation project has been converting the four sub-surface lines to automatic train operation using
communications-based train control. Upon completion of the project, there will be more frequent service as well as faster journey times. The section between Latimer Road and Hammersmith was the first to be switched over to automatic operation on 10 March 2019, with further extensions being implemented in stages called
Signal Migration Areas (SMA); as of January 2023 the first six SMA areas have been implemented. Due to various reasons such as funding and technical difficulties, District line automation where it shares tracks with Network Rail or Piccadilly line services has been scaled back until further notice. , trains are manually operated on most of the Metropolitan line and about half of the District line; the Circle and Hammersmith & City lines are fully automatic. ==Accidents and incidents==