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 London line extension station closed permanently to facilitate work on the extension, with services from Whitechapel being replaced by buses. The rest of the East London line closed on 22 December 2007, with rail replacement buses linking the stations north and south of the Thames (but not crossing the river due to height restrictions in the Rotherhithe Tunnel). On 5 September 2006 it was announced that the line would transfer from London Underground to London Overground, branded with a version of the Underground roundel with red replaced by orange, the colour used on Tube maps for the East London Line. Three major new