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 1986 Stock consultation results show that the blue prototype was the favoured, and provided the core design basis for the 1992 Stock that was built for London Underground's Central line and Network SouthEast's Waterloo & City line. London Underground 1986 Stock The London Underground 1986 Tube Stock consisted of three prototype electric multiple units built for London Underground that led to the development of the 1992 Stock. In 1984, London Transport ordered three different prototype trains to test new materials, construction methods and seating layouts. Two were built by Metro-Cammell at its Washwood Heath factory, and the third by British Rail Engineering