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 outside Heathrow Airport consistently records the highest number of daily traffic counts on the British strategic road network with a sample in 2017 measuring 211,059 counts (lower than the record peak measured in 2014 of 262,842 counts). This compares to 197,219 counts measured on the M1 motorway between junction 7 and 8 outside Hemel Hempstead in 2014, and 195,325 counts measured on the M60 motorway between junctions 12 and 13 in Western Manchester, also in 2014. The M25, plus the short non-motorway A282 which joins the two ends of the M25 across the River Thames using the Dartford Crossing, is