M25 (motorway)

The M25 motorway is one of the United Kingdom's motorways. It is an orbital motorway, 117 miles (188 km) in circumference, that almost completely encircles London (the gap is formed in the east, with the Dartford Crossing or the A282, linking two sides of the River Thames). It is said to be one of the longest city bypasses in the world. In Europe, the M25 is the second-longest ring road after the Berlin Ring (A 10) which is longer by 5 miles (8 km).

Description
For most of its length the motorway has six lanes (three in each direction), although there are a few short stretches which are four-lane and perhaps one sixth is eight-lane, around the south-western corner. The motorway was widened to ten lanes between junctions 12 and 14, and twelve lanes between junctions 14 and 15, in November 2005. The Highways Agency has plans to widen almost all of the remaining stretches of the M25 to eight lanes.

It is one of Europe's busiest motorways, with 196,000 vehicles a day recorded in 2003 between junctions 13 and 14 near London Heathrow Airport, which is however significantly fewer than the 257,000 vehicles a day recorded in 2002 on the A4 motorway at Saint-Maurice, in the suburbs of Paris , or the 216,000 vehicles a day recorded in 1998 on the A 100 motorway near the Funkturm in Berlin.

The M25 is not a continuous loop. To the east of London, the toll crossing of the Thames between Thurrock and Dartford is the lesser grade A282. The Dartford 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, dependent upon the type of vehicle. Designating this stretch as a motorway would mean that traffic not permitted to use motorways could not cross the Thames east of Woolwich.

While this is more a structural than a logical issue, at junction 5 near Sevenoaks continuing around the M25 requires the driver to follow the slip roads, as the anticlockwise carriageway continues as the M26 to the east (towards the M20) and the clockwise as the A21 towards the south coast.

The road passes through multiple police force areas. Junctions 1–5 are in Kent, 6–14 in Surrey (passing at 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 distance of the motorway from central London (taken as Charing Cross) varies from approximately 12 miles (20 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 while in others, most notably in Surrey, it is many miles distant. North Ockendon is the only settlement of Greater London to be outside the M25. In 2004, following a poll, a move was mooted by the London Assembly to entirely align the Greater London boundary to the M25.

The three service areas are located in the central north (JCT 23 South Mimms), south east (Clacket Lane) and central east (Thurrock).

History
The idea of an orbital road around London was first proposed early in the 20th century and was re-examined a number of times during the first half of the 20th century in plans such as Sir Edwin Lutyens and Sir Charles Bressey's The Highway Development Survey, 1937 and Sir Patrick Abercrombie's County of London Plan, 1943 and Greater London Plan, 1944. Abercrombie's plan proposed a series of five roads encircling the capital.

In the post-war years little was done to implement Abercrombie's plans but in the 1960s the Greater London Council developed an ambitious plan for a network of ring roads around the capital. The London Ringways plan was hugely controversial due to the destruction required for the inner two ring roads and the enormous anticipated cost. The plan was modified a number of times to overcome opposition from the residents of threatened areas and the government, but was cancelled in 1973. Parts of the two outer ring roads, Ringways 3 and 4, were begun in 1973 and became the first two sections of the M25 to open in 1975 (junction 23 to junction 24) and 1976 (junction 6 to junction 8).The M16 motorway was the designation planned in the late 1960s and early 1970s for use on Ringway 3, a new motorway planned as part of the London Ringways Plan to run a circular route around London.

Construction of the first section of the M16 began in 1973 between South Mimms and Potters Bar in Hertfordshire and opened in September 1975 with the temporary general purpose road designation A1178. During construction of the first section of the motorway, the majority of the Ringways plan was cancelled and, in 1975 the plans for Ringway 3 were modified to combine it with parts of another motorway, Ringway 4, the outermost Ringway.

The M16 designation was dropped and the combined motorway was given the designation M25 which had originally been intended for the southern and western part of Ringway 4. The section of Ringway 3 west of South Mimms anti-clockwise around London to Swanley in Kent was cancelled and the section clockwise from Potters Bar to the Dartford Tunnel was constructed between 1979 and 1982. The section of Ringway 3 south of the river between Dartford and Swanley was constructed between 1974 and 1977.

Construction of the M25 continued in stages until its completion in 1986. The stages were not constructed contiguously but in small sections, such as Dartford to Swanley (junction 1 to junction 3) and Potters Bar to Enfield (junction 24 to junction 25). As the orbital road developed the sections were linked. Each section was presented to planning authorities in its own right and was individually justified, with almost 40 public inquiries relating to sections of the route. Maps at this time depicting these short sections named the route as the M16 but this changed before completion. The northern sections of the M25 follow a similar route to the World War II Outer London Defence Ring.

The M25 was officially opened on 29 October 1986 with a ceremony by Prime Minister Margaret Thatcher, who opened the section between J22 and J23 (London Colney and South Mimms).

The initial tenders for the construction of the M25 totalled £631.9 million. This did not include compulsory purchase of land and subsequent upgrades and repairs.

More recently, the perennially congested south-western stretch of the M25 (near Woking) has been fitted with an experimental automated traffic control system called Motorway Incident Detection and Automatic Signalling (MIDAS). This consists of a distributed network of traffic and weather sensors, speed cameras and variable-speed signs that control traffic speeds with little human supervision, but has done little to alleviate traffic problems.

A precursor of the M25 was the North Orbital Road (see A414 road).

Improvements
When built the section of the M25 from just west of Junction 25 (A10/Waltham Cross) through to the eastern end of the Holmsdale Tunnel had only 2 lanes for motorway traffic. This was found to cause hold-ups at peak times as the majority of traffic approaching the junction did not leave the motorway. As a result a series of works, which were completed ahead of schedule in late 2007, have increased the number of lanes through this section from 2 to 3 in both clockwise and anti-clockwise directions. This work also included extending the Holmsdale Tunnel to the east.

In summer 2007 work started on widening the exit slip-roads in both directions at Junction 28 (A12/Brentwood). This is intended to reduce the amount of traffic queueing on the slip roads at busy periods, particularly traffic from the clockwise M25 joining the northbound A12 where the queue can extend onto the inside lane of the Motorway. The works included a dedicated left-turn lane from the M25 clockwise exit slip road to the A12 entry slip road. These works were completed in February 2008.

Widening
The Highways Agency is proposing to widen 63 miles of M25 from six lanes to eight lanes, from junctions 5-7 and 16-30 at a cost of over £5 billion. The Highways agency offering the contract on a Design, Build, Finance and Operate (DBFO) basis. A shortlist of contractors was announced in October 2006, however contractors were then asked to resubmit their bids in January 2008.

Illuminated sections
Large sections of the M25 are illuminated with the aim of reducing accidents on the road. The current illuminated sections are Dartford to junction 2, junction 5, junctions 6 to 16, junctions 18 to 21A, and junctions 23 to 31. It is thought that when the widening of the M25 is completed junctions 3 to 5 will be the only area unlit, as this is the quietest part of the M25. The type of lights on the M25 varies, with some of the sections using the older yellow low-pressure sodium (SOX) lighting, and others with modern high-pressure sodium (SON) lighting.

Some stretches have recently been upgraded to SON. These include Junction 5, junctions around Heathrow and 27.

Racing
The orbital nature of the motorway, in common with racetracks, lent itself to unofficial, and illegal, motor racing. At the end of the 1980s, before the advent of speed enforcement devices, owners of supercars, many employed in the financial service industry in the City and in Docklands, would meet at night at services stations such as South Mimms and conduct time trials. Times below 1 hour were achieved; an average speed of over 117 mph (188.3 km/h), which included coming to a halt at the Dartford Tunnel toll payment booths.

Public awareness and references in popular culture
The M25 (including the A282 Dartford Crossing) is known for its frequent traffic jams. These have been the subject of so much comment from such an early stage that even at the official opening ceremony Margaret Thatcher complained about "those who carp and criticise". The jams have inspired jokes ("the world's biggest car park", "the London Orbital Car Park"), songs (Chris Rea's "The Road to Hell") and the following tongue-in-cheek theory:

"Many phenomena – wars, plagues, sudden audits – have been advanced as evidence for the hidden hand of Satan in the affairs of Man, but whenever students of demonology get together the M25 London orbital motorway is generally agreed to be among the top contenders for exhibit A."

- from Good Omens, by Terry Pratchett and Neil Gaiman.''

This is because (in the book) the M25 was actually moulded by demonic forces during its planning so as to resemble, from space, a mystic demonic sigil.

Similar roads

 * Berlin A10
 * Dublin M50
 * Manchester M60
 * Paris Périphérique
 * Paris A86 autoroute
 * Rome Grande Raccordo Anulare
 * Moscow MKAD
 * Johannesburg Ring Road (N1, N3, N12)
 * Washington I-495 (the Capital Beltway)
 * Toronto Highway 407 ETR
 * São Paulo Rodoanel Mário Covas
 * Campinas (São Paulo, Brazil) Anel Viário José Magalhães Teixeira
 * Santiago Avenida Americo Vespucio