M25 motorway

M25 shield

London Orbital Motorway
Junction 13 looking south
Route information
Part of and
Maintained by Highways England
Length117 mi (188 km)
HistoryOpened: 1975
Completed: 1986
Major junctions
Orbital around London (in conjunction with the A282)
South endDarenth
 Junction 3.svg UK-Motorway-M20.svg
J3 → M20 motorway
Junction 5.svg UK-Motorway-M26.svg
J5 → M26 motorway
Junction 7.svg UK-Motorway-M23.svg
J7 → M23 motorway
Junction 12.svg UK-Motorway-M3.svg
J12 → M3 motorway
Junction 15.svg UK-Motorway-M4.svg
J15 → M4 motorway
Junction 16.svg UK-Motorway-M40.svg
J16 → M40 motorway
Junction 21.svg UK-Motorway-M1.svg
J21 → M1 motorway
Junction 23.svg UK-Motorway-A1 (M).svg
J23 → A1(M) motorway
Junction 27.svg UK-Motorway-M11.svg
J27 → M11 motorway
North endAveley
CountiesKent, Surrey, Berkshire, Greater London, Buckinghamshire, Hertfordshire, Essex
Heathrow Airport
St Albans
Road network

The M25 or London Orbital Motorway is 117 miles (188 km) long encircling almost all of Greater London, England (with the exception of North Ockendon). 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, aka London Ring Road, finally completed in 1986.

It is one of the busiest of the British motorway network: the stretch between Junctions 14 and 15 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).[1] 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 Europe's second longest orbital road after the Berliner Ring, which is 122 miles (196 km).


Carriageway widths of the M25 November 2009
The M25 and Heathrow Airport

Originally built almost wholly as a dual three-lane motorway, much of the motorway has been widened: to dual four lanes for almost half, to a dual five-lanes section between junctions 12 and 14 and a dual six-lane section between junctions 14 and 15. Further widening is in progress of minor sections with plans for managed motorways in many others.[2]

To the east of London the two ends of the M25 are joined to complete a loop by the non-motorway A282 Dartford Crossing of the River Thames between Thurrock and Dartford. This crossing, which consists of twin two-lane tunnels and the four-lane QE2 (Queen Elizabeth II) bridge, is named Canterbury Way. Passage across the bridge or through the tunnels is subject to a toll, its level depending on the kind of vehicle. This stretch being non-motorway, it allows traffic, including that not permitted to use motorways, to cross the River Thames east of the Woolwich Ferry; the only crossing further to the east is a passenger ferry between Gravesend, in Kent, and Tilbury, in Essex. However, in 2017 Highways England published plans to build another motorway-grade Thames tunnel to the east of Gravesend and Grays, the Lower Thames Crossing, in order to relieve congestion on the A282 Dartford Crossing and connect the M25 at North Ockendon in Essex with the M2 in Kent.[3]

At Junction 5, the clockwise carriageway of the M25 is routed off the main north–south dual carriageway onto the main east–west dual carriageway with the main north–south carriageway becoming the A21. In the opposite direction, to the east of the point where the M25 diverges from the main east–west carriageway, that carriageway become the M26 motorway.[4]

The radial distance from London (taken as Charing Cross) varies from 12.5 miles (20.1 km) in Potters Bar to 19.5 miles (31.4 km) in Byfleet. Three Greater London boroughs (Enfield, Hillingdon and Havering) have realigned their boundaries to the M25 for minor stretches; while in others, most notably in Essex and Surrey, the radial gap between Greater London and the motorway reaches 7.8 miles (12.6 km),[5] neither of which coincide with the Metropolitan Green Belt. Major towns listed as destinations (right), in various counties, adjoin the M25. North Ockendon is the only settlement of Greater London situated outside the M25. In 2004, following an opinion poll, the London Assembly mooted for consultation alignment of the Greater London boundary with the M25.[6] "Inside the M25" and "outside/beyond the M25" are colloquial, looser alternatives to "Greater London" sometimes used in haulage. 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.[7]

Two motorway service areas are on the M25, and two others are directly accessible from it. Those on the M25 are Clacket Lane between junctions 5 and 6 (in the south-east) and Cobham between junctions 9 and 10 (in the south-west). Those directly accessible from it are South Mimms off junction 23 (to the north of London) and Thurrock off junction 31 (to the east of London). Cobham services opened on 13 September 2012.[8][9]

Originally, the M25 was unlit except for sections around Heathrow, major interchanges and Junctions 23–30. Originally, low pressure sodium (SOX) lighting was the most prominent technology used, but widening projects from the 1990s onwards have all used high-pressure sodium (SON) lighting and this has diminished the original installations. By 2014 only one significant stretch was still SOX-lit (Junction 25–26) and the units were removed the same year.

The motorway passes through five counties. Junctions 1A–5 are in Kent, 6–14 are in Surrey, 15–16 are in Buckinghamshire, 17–25 are in Hertfordshire, and 26–31 are in Essex. Policing of 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, a maximum of 196,000 vehicles a day were recorded on the motorway just south of London Heathrow Airport between junctions 13 and 14.[10]

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