London Underground 1992 Stock & City line, which until 1994 was part of the national railway network, and became their Class 482. When this line passed to London Underground at the start of the process to privatise British Rail on 1 April 1994, these units also passed to London Underground. The vehicles are essentially identical to those used on the Central line; the main difference being that trip-cocks are used for protection instead of ATO/ATP. Transport for London and Metronet closed the Waterloo & City line for five months from April to September 2006 to allow major upgrade work on the tunnels and rolling
London Underground cells". The Waterloo and City Railway opened in 1898, followed by the Central London Railway in 1900, known as the "twopenny tube". These two ran electric trains in circular tunnels having diameters between and , whereas the Great Northern and City Railway, which opened in 1904, was built to take main line trains from Finsbury Park to a Moorgate terminus in the City and had diameter tunnels. While steam locomotives were in use on the Underground there were contrasting health reports. There were many instances of passengers collapsing whilst travelling, due to heat and pollution, leading for calls to clean