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
R25 (London) R25 (London) R25 is a possible railway orbital around the Zone 3 area of London, England. The proposed line would use some existing lines by National Rail and London Overground. Issue 755 of "Rail Magazine" (20 August 2014) says that the Mayor of London has started consulting on a new Zone 3 orbital railway, the 'R25'. The nickname alludes to the M25 orbital motorway. The idea featured in news media when the Mayor visited Barking Riverside a large development held up by lack of rail access. The idea of extending the Gospel Oak to Barking Line trains onto the Tilbury