M25 Motorway - Description

Description

Originally built mainly as a dual three-lane motorway, much of the motorway has subsequently been widened to dual four-lanes in places and to a dual five-lane section between junctions 12 and 14 and a dual six-lane between junctions 14 and 15. Further widening is in progress with plans for managed motorways on other sections.

The M25 is not a continuous loop. To the east of London, the Dartford Crossing of the Thames between Thurrock and Dartford has the non-motorway classification A282; the Crossing, which consists of two tunnels and the QE2 (Queen Elizabeth II) bridge, is named Canterbury Way. Passage across the bridge or through the tunnels is subject to a toll, depending on the kind of vehicle. Making this stretch a motorway would prevent any traffic not permitted to use motorways from crossing the River Thames east of the Woolwich Ferry.

At junction 5 near Sevenoaks, drivers continuing around the M25 in either direction must follow the slip roads. The anticlockwise carriageway continues eastward as the M26 (towards the M20); the clockwise carriageway continues towards the south coast as the A21.

The distance of the motorway from central London (taken as Charing Cross) varies from about 12 miles (19 km) near Potters Bar to 20 miles (32 km) near Byfleet. In some places (Enfield, Hillingdon and Havering) the Greater London boundary has been realigned to the M25 for minor stretches; while in others, most notably in Essex and Surrey, it is many miles distant. Major towns such as Epsom, and Watford are within the M25. North Ockendon is the only settlement of Greater London situated outside the M25. In 2004, following an opinion poll, a move was mooted by the London Assembly to align the Greater London boundary with the M25. "Inside the M25" and "outside the M25" or "beyond the M25" are used colloquially to refer to London and the provinces; the Communications Act 2003 explicitly uses the M25 as the boundary in requiring a proportion of television programmes to be made outside the London area.

There are four Motorway service areas on the M25. These are located at South Mimms (to the north of London) Thurrock (to the east), Clacket Lane (to the south-east) and Cobham (to the south-west). Cobham services were opened on 13 September 2012.

Much of the M25 is lit to help reduce accidents. The current illuminated sections are from Dartford to junction 3, junction 5, junctions 6 to 21a and junctions 23 to 31. The type of lighting varies. Some sections use the older yellow low-pressure sodium (SOX) lighting while others use modern high-pressure sodium (SON) lighting. Some stretches have recently been upgraded to SON lighting. These include Junction 5, junctions around Heathrow and Junction 27.

The motorway passes through several police areas. Junctions 1–5 are in Kent, 6–14 in Surrey (passing in places through Greater London and Berkshire), 15–16 are in Buckinghamshire, 17–24 are in Hertfordshire, 25 in Greater London (the Hertfordshire border going around the junction's northern edge), 26–28 in Essex, 29 in Greater London and 30–31 in Essex. Policing the road is carried out by an integrated policing group made up of the Metropolitan, Thames Valley, Essex, Kent, Hertfordshire and Surrey forces.

The M25 is one of Europe's busiest motorways. In 2003, 196,000 vehicles a day were recorded on the motorway near London Heathrow Airport between junctions 13 and 14.