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S7 and S8 Stock
A Metropolitan line S8 Stock at Amersham
The interior of a Circle line S7 Stock
In service	31 July 2010 − present
Manufacturer	Bombardier Transportation
Built at	Derby Litchurch Lane Works
Family name	Movia
Replaced	A60/62 Stock C69/77 Stock D78 Stock
Constructed	2009–2017
Number built	192 trains (S8: 58, S7: 134)
Number in service	192 trains
Formation	S7: 7 cars per train S8: 8 cars per train
Capacity	S7: 851 S8: 1176
Operator(s)	London Underground
Depot(s)	Ealing Common Neasden Upminster Hammersmith (sidings only) Lillie Bridge (sidings only)
Line(s) served	S7: Circle line District line Hammersmith & City line S8: Metropolitan line
Specifications
Car body construction	Aluminium
Train length	117.45 m (385 ft) (S7) 133.68 m (439 ft) (S8)
Car length	17.44 m (57 ft) (DM) 15.43 m (51 ft) (NDM)
Width	2.92 m (9 ft 7 in)[1]
Entry	Level
Doors	Six per carriage
Maximum speed	100 km/h (62 mph)
Traction system	IGBT-VVVF (Bombardier MITRAC)
Acceleration	1.3 m/s2
Electric system(s)	750 V DC fourth rail
Current collection method	Contact shoe
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge
Notes
London transport portal

The London Underground S7 and S8 Stock, commonly referred to as S Stock, is a type 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. The order consists of a total of 192 trains (1,402 cars), and consists of two types, S7 Stock and S8 Stock, 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 also have open gangways to allow passengers to move from one car to another whilst the train is moving.

The order is said to be the biggest single rolling-stock order in Britain^[2] at, according to Transport for London, a cost of £1.5 billion.^[3]

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.

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,^[4] the C Stock on the Circle line and Hammersmith & City line,^[5] and D Stock on the District line.^[6]

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 were also three additional eight-car trains called an S7+1 in use on the Metropolitan Line while the eight-car S8 trains were returned for engineering modifications and ATC fitment. These trains were formed of a seven-car S7 and an additional car from another S7, forming an eight-car train. This train, however, retained the all-longitudinal seating of the S7, and thus could be distinguished from the remaining S8s. These trains were modified back to seven-car trains and transferred for service on the Circle, District and Hammersmith & City Lines in 2018.^{[citation needed]} The S8 Stock entered service between 2010 and 2012, operating all services by September 2012.

The S Stock has faster acceleration than previous trains, 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 had 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.^[2]

The voltage has been increased from nominal 630 volts to 750 volts. This allows 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.^[1]

At present S Stock is operated manually, but London Underground will activate automatic train operation once the necessary signalling is in place, starting in mid-September 2018.^[7]

Features

Selective door operation (SDO) is used at some stations where it is not feasible to extend the platform, such as Baker Street

The S Stock is air-conditioned throughout: the sub-surface tunnels (unlike deep-level tube lines) allow the exhausted hot air to disperse,^[2] and two-thirds of the sub-surface network is in the open air.^[8] The stock has regenerative brakes, returning around 20% of their energy to the network and thus increasing energy efficiency.^[9]

S8 Stock during testing near Northwood

Gangway connection between cars

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 supplied by Mitsubishi and has two circuits so that if one fails there is still 50% capacity.^[8] Through gangways from car to car are another innovation, as on 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.^[8] There is a fold-out set of steps in each driver's cab to allow fast evacuation in an emergency.^[10]

The S stock has cantilevered seating for easy cleaning and accessible storage of bags.^[11] 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).^[12]

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

All S 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.^[13][14]

Entry into service

Metropolitan line

A London Underground S7 Stock train at Wood Lane operating a Circle line service.

The interior of a London Underground Metropolitan line S8 Stock train with transverse seats.

The interior of a London Underground Circle line S7 Stock train, showing the wheelchair parking places

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.^[8]

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.^[15]

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.^[16]

By 15 September 2012, all 58 S8 trains had been delivered to Neasden Depot.^{[citation needed]} The A Stock trains were completely withdrawn 11 days later.^{[citation needed]} 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.^[17]

Hammersmith & City line

C Stock (left) and S7 Stock (right) at Hammersmith station (H&C and Circle) in July 2013

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.^[8]

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.^[18] The line was completely operated with S7 stock by 10 February 2014.^{[citation needed]}

Circle line

S7 Stock entered service on the Circle line on 2 September 2013,^[19] and completely replaced the C Stock trains on the line on 10 February 2014.^{[citation needed]}

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.^[20]

District line

District line S7 Stock train at Kensington (Olympia) station, heading for West Ham

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. The S 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 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.^[21]

Naming

London Underground has named some S Stock Units.

• 21100 – Tim O'Toole CBE
  


• 21302 – Queen Elizabeth II
  

List of cars

Each car has a five-digit number: the second digit identifies the type of car, the last three digits the set number (001–116, 301–568). A-end cars have odd numbers; D-end even numbers. 25nnn cars replace 23nnn cars on trains equipped with de-icing equipment.

See also

• 
  Victoria line 2009 Tube Stock, also part of Bombardier's Movia family


• 
  London Overground Class 378
  

References

External links

Wikimedia Commons has media related to London Underground S7 and S8 Stock.

• S Stock data sheet


• 
  Vehicle 21100 on its way for testing at Old Dalby Test Track – part of the first set completed


• Article about the new S7 trains entering service onto the Hammersmith and City Line