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
M25 motorway unofficial, and illegal, motor racing. At the end of the 1980s, before the advent of speed enforcement devices, owners of supercars would meet at night at service stations such as South Mimms and conduct time trials. Times below 1 hour were achieved - an average speed of over 117 mph (188 km/h), which included coming to a halt at the Dartford Tunnel road user charge payment booths. Data from driver location signs provide carriageway identifier information. The numbers on the signs are kilometres from a point near the River Thames, east of London, when travelling clockwise on the motorway. The