London Underground S Stock

The London Underground S Stock is a fleet of subsurface rolling stock used on the London Underground since 2010. Manufactured by Bombardier Transportation's Derby Litchurch Lane Works, the S Stock was ordered to replace the A60, A62, C69, C77 and D78 stock on the Metropolitan, District, Hammersmith & City, and Circle lines, which all date back to the 1960s and 1970s. It was supposed to be a straightened train, similar to the HK Zug trains in Berlin, and they are supposed to order 22 trains for the North South Line only in 2011, later it was dropped as they wanted to consolidate the order into C151A. The order consists of a standardised fleet of 191 trains (1,395 cars), with 1 additional train (8 cars) ordered as a part of Metropolitan line extension to Watford Junction (192 trains = 1,403 cars). The stock has two types, S7 and S8, serving different lines, with differences in the arrangement of seating and number of cars. Both types have air-conditioning and low floors to ease accessibility for disabled people, and it is also possible for a passenger to walk from one car to the next while the train is moving, unlike older trains on the network.

The order is said to be the biggest single rolling-stock order in Britain at, according to Transport for London, a cost of £1.5 billion.

Passenger service began on the Metropolitan line in July 2010, the Hammersmith & City line in July 2012, and the Circle and District lines in September 2013. The S Stock completely replaced the A Stock on the Metropolitan line in September 2012, and the C Stock on the Circle and Hammersmith & City lines in February 2014, and started operating on the District line in June 2014; it fully replaced the D Stock on the rest of the District line in April 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.

By 27 June 2011, S8 Stock was running along the whole Metropolitan line. Deliveries were suspended by Transport for London in November 2011 due to concerns over reliability. A number of trains were delivered to London Underground's Neasden depot, but were not accepted to enter service. Deliveries resumed in mid-December 2011.

In August 2012, London Underground confirmed that strap handles would be introduced on S8 Stock, in response to passenger complaints over the height of the handrails as compared with A Stock.

By 15 September 2012, all 58 S8 trains had been delivered to Neasden Depot. The A Stock trains were completely withdrawn 11 days later. 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 the driver's cabs.

Hammersmith & City line
The first trains entered service on 6 July 2012, from Hammersmith to Moorgate. S7 trains are longer than those they are replacing (seven cars and 117 m long instead of six cars and 93 m long), so some station platforms have to be lengthened before they can operate in normal service. For stations where this has proved physically impossible, such as, the trains have a selective-door-opening capability whereby the doors at the end of the train will not open.

On 4 December 2012, an S7 train went east of Moorgate to Barking for testing. This was the first time an S7 train had been seen in peak hours. S7 Stock began operating a full service from Hammersmith to Barking on 9 December 2012. The line was completely operated with S7 stock by 10 February 2014.

Circle line
S7 Stock entered service on the Circle line on 2 September 2013, and completely replaced the C Stock trains on the line on 10 February 2014.

The Circle line's C Stock were replaced ahead of the District line's D Stock, as they were described by London Underground as being "in an increasingly poor state", and the D Stock had been extensively refurbished between 2005 and 2008.

District line
The District line was the last line to be fully served by the S Stock, due to its existing D Stock being newer than other trains that the S Stock was ordered to replace, as well as its recent refurbishment. 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 S Stock started running between Wimbledon and Edgware Road. On 13 June 2014, the S Stock started services to Ealing Broadway and on 17 June saw the start of commercial service to Richmond. On 16 January 2015, the Stock began running to Upminster. Withdrawal of the D Stock began on 19 January.

The D Stock was completely replaced by the S7 with the withdrawal of the final unit from service on 21 April 2017.