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
East Rail line branches in the north at Sheung Shui to terminate at Lo Wu or Lok Ma Chau stations. Both are boundary crossing points into Shenzhen. All of the stations are at- grade or elevated before the opening of Shatin to Central Link which will provide underground track. The distance between Hung Hom and Lo Wu stations is . The total distance of the line (including the Lok Ma Chau Spur line) is approximately , making it the longest line in total distance within the system network. The line is coloured light blue on the MTR map. The same railway is used