London Underground infrastructure
The total length of railway on the London Underground is 400 kilometres (250 mi) and made up of the sub-surface network and the deep-tube lines.
[2][3] The Circle, District, Hammersmith & City, and Metropolitan lines are services that run on the sub-surface network, that has railway tunnels just below the surface and was built mostly using the cut-and-cover method.
[1] Trains generally run on the left-hand track, although in some places, for example the Central line east of St Paul's station, tunnels are dug one above each other.
[14] With the problem on the original line continuing after the 1880s, conflict arose between the Met, who wished to make more openings in the tunnels, and the local authorities, who argued that these would frighten horses and reduce property values.
The report recommended more openings be authorised but the underground sections of the Metropolitan and District railways were electrified before these were built.
However, soon after opening there were complaints about a smell that the company couldn't explain, and by 1911 they had installed a system of fans injecting filtered air and ozone.
[17] However, over time heat from the trains has warmed up the tube tunnels, and in 1938 approval was given to a £500,000 programme to improve the ventilation and an experimental refrigeration plant was installed in a lift shaft at Tottenham Court Road.
[20] A 2003 study stated that air quality was seventy-three times worse than at street level, with twenty minutes on the Northern line having "the same effect as smoking a cigarette".
[21] The main purpose of the London Underground's ventilation fans is to extract hot air from the tunnels,[18] a system on the Jubilee line extension being designed to allow cooling of the tubes at night.
Fans over the network are being refurbished, although complaints of noise from local residents preclude their use at full power at night.
A prize of £100,000 was offered by the Mayor of London during the hot summer of 2003 for a solution to the problem, but the competition ended in 2005 without a winner.
[1] The shortest distance between adjacent stations is the 330 yards (300 m) between Leicester Square and Covent Garden on the Piccadilly line.
The highest station is Amersham on the Metropolitan line, at 147 metres (482 ft) above sea level and the highest point above ground is the Dollis Brook Viaduct over Dollis Road between Finchley Central and Mill Hill East on the Northern line, 18 metres (59 ft) above the ground.
[1] When the City & South London Railway opened in 1890[32] access to the platforms was by two hydraulic lifts, each capable of carrying 50 passengers.
[37] Hydraulic lifts were provided at Finsbury Park, powered from the GN&CR pumping station,[38] and at Holloway Road there was an experimental spiral conveyor, but this was never used by the public.
[40] The Otis Seeberger design of escalator, with a diagonal shunt at the top landing requiring a sideways step off, was used until 1924, when the first 'comb' type was installed at Clapham Common.
[42] It is thought that people were standing on the right as the diagonal shunts at the top of the escalators made it easier to step off with the right foot.
[44] Before World War II, an escalator installed at Sloane Square was the first connecting Circle line platforms to the street, but it was destroyed when the station was hit by a bomb in 1940.
Due to wartime conditions, no escalators were provided when Highgate station on the Northern line extension opened in 1941; these were finally installed in 1957.
This was followed by the Fire Precautions (Sub-Surface Railway Stations) Regulations 1989 which required all wooden escalators on the Underground to be replaced with metal ones.
[46] Treads were originally maple wood, then aluminium from 1963, and this had been replaced with plastic or rubber following an increase in serious injuries following falls.
[50] Major efforts have taken place to improve accessibility across the Underground, with the Jubilee line extension having lifts from opening in 1999, and key interchange stations such as King's Cross St Pancras, Victoria and Green Park becoming step-free.
[58] New trains are designed for maximum number of standing passengers and for speed of access to the cars and have regenerative braking and public address systems.
[64] The London Borough of Hillingdon has proposed that the Central line be extended from West Ruislip to Uxbridge via Ickenham, claiming the extension would cut traffic on the A40 in the area.
