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
History of the London Underground were first installed at Earl's Court between the District and Piccadilly line platforms, and at all deep level tube stations after 1912. The last, the Charing Cross, Euston & Hampstead (the Hampstead) opened in 1907, and ran from to Camden Town, before splitting into two branches going to Golders Green and Highgate (now Archway). To promote travel by the underground railways in London a joint marketing arrangement was agreed that included maps, joint publicity and through ticketing. UD signs were used outside stations in Central London. The UERL acquired London bus and tram companies in 1912 and the following year