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
Central line (London Underground) GER on 1 May 1903. The line has three junctions: The line has the shortest escalator on the London Underground system, at Stratford (previously at Chancery Lane), with a rise of and at Stratford and Greenford the only stations where escalators take passengers up to the trains. That at Greenford was the last escalator with wooden treads on the system until it was replaced in March 2014. They were exempt from fire regulations because they were outside the tunnel system. The line has the shallowest Tube platforms on the system, at Redbridge, just below the road, and the sharpest curve,