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 Transport, and discontinued the use of the London Transport brand in favour of its own brand. The transfer of responsibility was staged, with transfer of control of the London Underground delayed until July 2003, when London Underground Limited became an indirect subsidiary of TfL. Between 2000 and 2003, London Underground was reorganised in a Public-Private Partnership where private infrastructure companies (infracos) upgraded and maintained the railway. This was undertaken before control passed to TfL, who were opposed to the arrangement. One infraco went into administration in 2007 and TfL took over the responsibilities, TfL taking over the other in 2010.