London Underground with smaller trains that run in two circular tunnels ("tubes") with a diameter about . These lines have the exclusive use of a pair of tracks, except for the Piccadilly line, which shares track with the District line between Acton Town and Hanger Lane Junction and with the Metropolitan line between Rayners Lane and Uxbridge; and the Bakerloo line, which shares track with London Overground services north of Queen's Park. Fifty-five per cent of the system runs on the surface. There are of cut-and-cover tunnel and of tube tunnel. Many of the central London underground stations on deep-level tube routes
Central line (London Underground) by escalators. The Central London Railway was absorbed into the Underground Group on 1 January 1913. In 1911, the Great Western Railway won permission for a line from Ealing Broadway to a station near to the CLR's Shepherd's Bush station, with a connection to the West London Railway, and agreement to connect the line to the Central London Railway and for the CLR to run trains to Ealing Broadway. Construction of the extension from the CLR to Ealing Broadway started in 1912 but opening was delayed by World War I. The CLR purchased new rolling stock for the extension, which