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
London Underground 1973 Stock London Underground 1973 Stock The London Underground 1973 Stock is a type of rolling stock used on the Piccadilly line of the London Underground. It was introduced into service in 1975 with the extension of the line to Hatton Cross, followed by a further extension to Heathrow Central in 1977. The trains were built by Metro-Cammell between 1974 and 1977, and were refurbished by Bombardier Transportation between 1996 and 2001. They are some of the oldest trains running on the Underground, second only to the 1972 Stock running on the Bakerloo line. In the early 1970s London Transport placed an