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
South London line South London line The South London line is an Inner London part of the London Overground rail network. The line is run together with the East London line to provide direct services between and . It consists of eight stations, one of which marks the crossover into the East London line network and runs . Most of the line is on high viaduct over other transport infrastructure. Interchanges with the London Underground are at and the closest on its London Overground extension is . The line is in Travelcard Zone 2. From the early 20th century until 2012 a shorter