London Underground S7 and S8 Stock

Overview

The S designation stands for sub-surface, following the London Underground tradition of designating surface stock with a letter associated with its intended route - A Stock on the Metropolitan line to Amersham, the C Stock on the Circle line and Hammersmith & City line, and D Stock on the District line.

Part of Bombardier's Movia family, the stock consists of 133 S7 seven-car trains for the Circle, District and Hammersmith & City lines and 58 S8 eight-car trains for the Metropolitan line. There is also one additional eight-car train called an S7+1 in use on the Metropolitan line, ordered as part of the Metropolitan Line extension to Watford Junction. This train is formed of a seven-car S7 and an additional car from another S7, forming an eight-car train. This train, however, retains the all-longitudinal seating of the S7, and thus can be distinguished from the remaining S8's. The S8 Stock entered service between 2010 and 2012, operating all services by September 2012.

The stock has faster acceleration than previous stock, at 1.3 m/s² (2.9 mph per second), but its top speed is 62 mph (100 km/h), 8 mph slower than A Stock but faster than C and D Stocks. During the period of dual operation with both old and new trains, the stock has its performance capped to match that of the older trains in order to comply with signalling constraints and avoid bunching of the service. S8 stock seats 306 passengers compared with 448 for A Stock, a reduction of 32%, but it can accommodate 25% more standing passengers (1,226 compared with 976) and has dedicated space for wheelchairs.

Eventually the voltage will be increased from nominal 630 volts to 750 volts. This will allow for better performance and also for the increased power demands of air-conditioned, fully motored-axle trains, and allow the trains to return energy to the network through regenerative braking.

At present the stock is operated manually, but London Underground will activate automatic train operation once the necessary signalling is in place by 2022. It was initially intended that the upgrade would happen in 2018, but has been delayed.

Features

The stock is air-conditioned throughout: the sub-surface tunnels (unlike deep-level tube lines) allow the exhausted hot air to disperse, and two-thirds of the sub-surface network is in the open air. The stock has regenerative brakes, returning around 20% of their energy to the network and thus increasing energy efficiency.

End external displays show two lines of text: the top line for the destination, and the bottom for the line. Internally, it has larger dot matrix indicators (DMIs) than D Stock (C Stock lacked DMIs, as did A Stock). The DMIs show destination and line, and can display other messages such as safety notices. There are also DMIs on the exterior, with text alternating between destination and line, and on S8 stock the type of service, i.e. fast, semi-fast or all stations.

Another new feature is that to prevent accidental pressing of emergency alarms there are flaps over the alarm buttons where the wheelchair spaces are.

The air-conditioning system, the first on London Underground trains, is by Mitsubishi and has two circuits so that if one fails there is still 50% capacity. Through gangways from car to car are another innovation, as on the London Overground's Class 378. This allows passengers to move from crowded cars to ones with more room, provides extra room for standing and creates a sense of security. CCTV enables the driver to see into every car, while track-to-train video links give the driver a view of the train exterior before leaving a station.

There is a fold-out set of steps in each driver's cab to allow fast evacuation in an emergency.

The stock has cantilevered seating for easy cleaning and accessible storage of bags. S7 Stock has longitudinal seating throughout, S8 a mix of transverse and longitudinal seating, with four wheelchair spaces per train. S7 Stock trains are 117.45 metres (385 ft 4 in) long, S8 133.68 m (438 ft 7 in).

The stock is the first on the Metropolitan line with dot-matrix indicators and automated voice announcements.

All stock can operate on all sub-surface lines, with selective door operation used at stations that are shorter than the train. S8 Stock operates as an eight-car formation while S7 Stock operates as a seven-car formation.

Design icon

As part of the Transported by Design programme of activities, on 15 October 2015, after two months of public voting, the walk-through S-Stock train was elected by Londoners as one of the 10 favourite transport design icons.

Metropolitan line

S8 Stock was initially tested overnight between Amersham and Watford 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 Baker Street, 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 will be 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 due to be completely replaced by the end of December 2016., but as of February 2017 nine D Stock trains are still in use.

Roster

This section describes the roster of S Stock trains.

Cars have a five-digit number: the second digit identifies the role of car, the last three digits the set number (001 - 116, 301 - 567). A-end cars have odd numbers, D-end even numbers.