Portal:London transport/Selected articles/61
The M25 or London Orbital Motorway is a 117-mile (188 km) motorway that encircles almost all of Greater London, England (with the exception of North Ockendon), in the United Kingdom. An ambitious concept to build four concentric ring roads around London was first mooted in the 1960s. A few sections of the outer two rings were constructed in the early 1970s, but the plan was abandoned and the sections were later integrated to form a single ring which became the M25, completed in 1986.
It is one of the busiest of the British motorway network: 196,000 vehicles were recorded on a busy day near Heathrow Airport in 2003 and the western half experienced an average daily flow of 147,000 vehicles in 2007. To alleviate congestion, sections of the motorway have been widened from the original three-lane carriageways to four-, five- or six-lane carriageways. Other sections use Smart motorway operation with hard shoulders replaced with standard lanes.
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 Europe's second longest orbital road after the Berliner Ring, which is 122 miles (196 km).