Automation of the London Underground Automation of the London Underground Automation of London Underground rolling stock has been partially implemented since the introduction of automatic train operation on the Hainault to Woodford section of the Central line in 1964. It is currently in use on four lines. Transport for London plans to extend this to other lines by 2022. Partially automated trains using Automatic Train Operation (ATO) have been used on passenger services on the Victoria line since 1968. The side doors to the driver's cab were sealed, so that access was normally through the passenger saloon. Since the trains were to be operated by
Circle line (London Underground) with the other London Underground sub-surface lines: the Hammersmith & City line from Hammersmith to just before Aldgate; the Metropolitan line from Baker Street to Aldgate; and the District line from Tower Hill station to Edgware Road station. The line is electrified with a four-rail DC system: a central conductor rail is energised at and a rail outside the running rail at , giving a potential difference of . The running rails are not electrified. Much of the double track railway from the Hammersmith terminus to Westbourne Park station is on a high brick viaduct. East of Westbourne Park the