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 fare zones W. On maps these stations are shown as being outside fare zones 1–9 but within the 'special fares' Oyster pay as you go area. In January 2016, the Oyster and contactless system was extended to Gatwick Airport in Crawley, West Sussex, and the stations down that line (Horley, Salfords, Earlswood, Redhill and Merstham). London fare zones Rail service fares in Greater London and the surrounding area are calculated in accordance with the London fare zones system managed by Transport for London. Within London, all London Underground, National Rail, London Overground, TfL Rail and Docklands Light Railway stations are assigned to