Editing M25 motorway

{{Short description|Orbital motorway around Greater London}}
{{Good article}}
{{Use dmy dates|date=October 2023}}
{{Use British English|date=February 2013}}
{{Infobox road
| country = GBR
| type = M
| route = 25
| alternate_name = London Orbital Motorway
| map = {{switcher
   | {{maplink-road |from1=M25 motorway.map |from2=Dartford Crossing.map}}{{legend-line|#0066CC solid 3px|M25 motorway|inline=yes}}   {{legend-line|#00CC00 solid 3px|A282 Dartford Crossing|inline=yes}}{{hr}}
   | Show interactive map
   | [[File:M25 motorway (Great Britain) map.svg|frameless|x323px]]<br />Shown with the UK motorway network{{hr}}
   | Show UK motorways map
   }}
| map_custom = yes
| map_notes = 
| photo = Egham M25 aerial 2011.jpg
| photo_notes = Junction 13 looking south, 2011
| e-road = {{Jct|country=EUR|E|15}} and {{Jct|country=EUR|E|30}}<ref name="AAAtlas">{{cite book |title=Big Road Atlas Europe 2020 |author=AA Publishing |year=2019}}</ref>
| maint = Connect Plus (contracted to [[National Highways]])
| length_km = 188
| established = 1975
| history = Opened: 1975<br />Completed: 1986
| orbital = [[London]] (in conjunction with the [[Dartford Crossing|A282]])
| direction_a = Anti-clockwise
| terminus_a = [[Dartford]] ([[Dartford Crossing]] southern approach)
| junction = [[File:Junction 3.svg|1000x20px]] [[File:UK-Motorway-M20.svg|1000x20px]]<br />J3 → [[M20 motorway]]<br />[[File:Junction 5.svg|1000x20px]] [[File:UK-Motorway-M26.svg|1000x20px]]<br />J5 → [[M26 motorway]]<br />[[File:Junction 7.svg|1000x20px]] [[File:UK-Motorway-M23.svg|1000x20px]]<br />J7 → [[M23 motorway]]<br />[[File:Junction 12.svg|1000x20px]] [[File:UK-Motorway-M3.svg|1000x20px]]<br />J12 → [[M3 motorway (Great Britain)|M3 motorway]]<br />[[File:Junction 15.svg|1000x20px]] [[File:UK-Motorway-M4.svg|1000x20px]]<br />J15 → [[M4 motorway]]<br />[[File:Junction 16.svg|1000x20px]] [[File:UK-Motorway-M40.svg|1000x20px]]<br />J16 → [[M40 motorway]]<br />[[File:Junction 21.svg|1000x20px]] [[File:UK-Motorway-M1.svg|1000x20px]]<br />J21 → [[M1 motorway]]<br />[[File:Junction 23.svg|1000x20px]] [[File:UK-Motorway-A1 (M).svg|1000x20px]]<br />J23 → [[A1(M) motorway]]<br />[[File:Junction 27.svg|1000x20px]] [[File:UK-Motorway-M11.svg|1000x20px]]<br />J27 → [[M11 motorway]]
| direction_b = Clockwise
| terminus_b = [[Thurrock]] ([[Dartford Crossing]] northern approach)
| counties = [[Kent]], [[Surrey]], [[Berkshire]], [[Greater London]], [[Buckinghamshire]], [[Hertfordshire]], [[Essex]]
| destinations = [[London]]<br />[[Dartford Crossing]]<br />[[Sevenoaks]]<br />[[Gatwick Airport]]<br />[[Heathrow Airport]]<br />[[Watford]]<br />[[London Stansted Airport|Stansted Airport]]<br />[[Brentwood, Essex|Brentwood]]
<br />[[Chelmsford, Essex|Chelmsford]] <br />[[Ilford, Essex|Ilford]] <br />[[Romford, Essex|Romford]] 
| previous_type = M
| next_type = M
| previous_route = 23
| next_route = 26
}}

The '''M25''' or '''London Orbital Motorway''' is a major road encircling most of [[Greater London]]. The {{convert|117|mi|km|0|adj=mid|-long}} motorway is one of the most important roads in the UK and one of the busiest. [[Margaret Thatcher]] opened the final section in 1986, making the M25 the longest [[ring road]] in Europe upon opening.{{efn|name=Berliner_Ring_is_longer}} The [[Dartford Crossing]] completes the orbital route but is not classed as motorway; it is classed as a [[trunk road]] and designated as the [[A282]]. In some cases, including notable legal contexts such as the [[Communications Act 2003]], the M25 is used as a ''[[de facto]]'' alternative boundary for Greater London.

In the 1944 ''[[Greater London Plan]]'', [[Patrick Abercrombie]] proposed an orbital motorway around London. This evolved into the [[London Ringways]] project in the early 1960s, and by 1966, planning had started on two projects, [[London Ringways#Ringway 3|Ringway 3]] to the north and [[London Ringways#Ringway 4|Ringway 4]] to the south. By the time the first sections opened in 1975, it was decided the ringways would be combined into a single orbital motorway. The M25 was one of the first motorway projects to consider environmental concerns and almost 40 public inquiries took place. The road was built as planned despite some protests that included the section over the [[North Downs]] and around [[Epping Forest]] which required an extension of the [[Bell Common Tunnel]].

Although the M25 was popular during construction, it quickly became apparent that there was insufficient traffic capacity. Because of the public inquiries, several junctions merely served local roads where office and retail developments were built, attracting even more traffic onto the M25 than it was designed for. The congestion has led to traffic management schemes that include [[variable speed limit]] and [[smart motorway]]. Since opening, the M25 has been progressively widened, particularly near [[Heathrow Airport]].

==Description==
===Route===
[[File:070921-Final DLS map.pdf|thumb|left|300px|Map of the M25 showing the junction numbers and driver location signs]]

The M25 almost completely encircles [[Greater London]] and passes briefly through it, in the east and west.<ref>{{cite web | url = https://s3-eu-west-2.amazonaws.com/lgbce/Reviews/Greater%20London/Havering/(SI%202021-000)%20-%20Draft%20LB%20of%20Havering%20(Electoral%20Changes)%20Order%20Map.pdf | title = Map referred to in the London Borough of Havering (Electoral Changes) Order 2021 | year = 2021 | website = [[Boundary commissions (United Kingdom)|The Local Government Boundary Commission for England]] | access-date = 27 October 2022 | archive-url = https://web.archive.org/web/20220406201316/https://s3-eu-west-2.amazonaws.com/lgbce/Reviews/Greater%20London/Havering/(SI%202021-000)%20-%20Draft%20LB%20of%20Havering%20(Electoral%20Changes)%20Order%20Map.pdf | archive-date = 6 April 2022}}</ref><ref name=Heathrow>{{cite web | url = https://hillingdon.gov.uk/media/7977/Heathrow-Villages-ward/pdf/Heathrow_Ward.pdf | title = Heathrow Villages ward map | year = 2022 | website = [[London Borough of Hillingdon]] | access-date = 27 October 2022 | archive-url = https://web.archive.org/web/20220525121027/https://www.hillingdon.gov.uk/media/7977/Heathrow-Villages-ward/pdf/Heathrow_Ward.pdf | archive-date = 25 May 2022}}</ref> Junctions 1A–5 are in [[Kent]], 6–13 are in [[Surrey]], 14 and a small part of 15 are in [[London Borough of Hillingdon|Hillingdon]], Greater London, 15–16 are in [[Buckinghamshire]], 17–24 are in [[Hertfordshire]], 25 is in [[London Borough of Enfield|Enfield]], Greater London and 26–31 are in [[Essex]].<ref name=Heathrow /> Law enforcement on the road is carried out by an integrated group made up of the [[Metropolitan Police Service|Metropolitan]], [[Thames Valley Police|Thames Valley]], [[Essex Police|Essex]], [[Kent Police|Kent]], [[Hertfordshire Constabulary|Hertfordshire]] and [[Surrey Police|Surrey]] police services.{{sfn|Hamilton|2015|p=24}} [[Roads in the United Kingdom#Primary destinations|Primary destinations]] signed ahead on the motorway include the [[Dartford Crossing]], [[Sevenoaks]], [[Gatwick Airport]], [[Heathrow Airport]], [[Watford]], [[London Stansted Airport|Stansted Airport]] and [[Brentwood, Essex|Brentwood]].<ref>{{cite web|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/203664/traffic-signs-manual-chapter-02-primary-route.pdf|title=Traffic Signs Manual Chapter 2 : Primary Routes|publisher=Department of Transport|access-date=14 May 2019}}</ref>

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]]. The crossing consists of twin two-lane tunnels and the four-lane [[QE2 Bridge|QE2 (Queen Elizabeth II) bridge]],<ref name=AATrust>{{cite web|url=http://www.theaa.com/public_affairs/reports/dartford_tunnel_test_2004.pdf|title=Tunnel Test 2004 – Dartford Tunnel|date=September 2004|page=3|publisher=[[AA Motoring Trust]]|access-date=22 May 2010|archive-url=https://web.archive.org/web/20170108211825/http://www.theaa.com/driving-advice/driving-costs/dartford-crossing-dart-charge|archive-date=8 January 2017}}</ref><ref>{{cite web|url=https://pla.co.uk/Safety/Thames-Bridges-Heights|title=Thames Bridges Heights|publisher=Port of London Authority|access-date=7 August 2016}}</ref> with a main span of {{convert|450|m|ft}}.<ref>{{cite book|url=https://books.google.com/books?id=_h39X2cspQ0C&q=dartford+crossing+450+metres&pg=PA26|title=Bridge|first=Peter|last=Bishop|publisher=[[Reaktion Books]]|page=26|year=2008|isbn=978-1-861-89346-8}}</ref> Passage across the bridge or through the tunnels is subject to a [[road pricing|charge]] between 6 am and 10 pm, its level depending on the kind of vehicle. The road is not under motorway regulations so that other traffic can cross the Thames east of the [[Woolwich Ferry]];{{efn|Pedestrians and cyclists cannot directly use the Dartford Crossing, but a shuttle service is available for the latter.<ref>{{cite web|url=https://www.gov.uk/dartford-crossing-bike|title=Get across the Dartford crossing by bike|work=HM Government|access-date=13 May 2019}}</ref>}} the only crossing further to the east is [[Gravesend-Tilbury Ferry|a passenger ferry]] between [[Gravesend]], [[Kent]], and [[Tilbury]], [[Essex]].<ref>{{cite news|url=https://www.kentonline.co.uk/gravesend/news/walk-on-to-cross-the-4983/|title=Walk on to cross the water|work=Kent Online|date=23 August 2013|access-date=14 May 2019}}</ref>

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 road (England)|A21]]. In the opposite direction, to the east of the point where the M25 diverges from the main east–west carriageway, that carriageway becomes the [[M26 motorway]].<ref name=J5>{{cite web|title = M25 in South East Region|publisher = The Motorway Archive|url = http://www.ukmotorwayarchive.org/|year = 2009|at = (Select "M25" from list of motorways, then "M25 interchanges, tunnels and bridges")|access-date = 18 April 2013}}</ref> From here to junction 8, the M25 follows the edge of the [[North Downs]] close to several historic buildings such as [[Chevening]], [[Titsey Place]], [[Hever Castle]] and [[Chartwell]].<ref name=leadbetter>{{cite news|url=https://www.telegraph.co.uk/travel/destinations/europe/united-kingdom/articles/m25-road-trip-best-sights/ |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/travel/destinations/europe/united-kingdom/articles/m25-road-trip-best-sights/ |archive-date=12 January 2022 |url-access=subscription |url-status=live|title=10 reasons why a lap of the M25 is Britain's ultimate road trip|newspaper=The Daily Telegraph|date=29 October 2016|access-date=28 May 2019}}{{cbignore}}</ref><ref name=barkham>{{cite news|url=https://www.theguardian.com/world/shortcuts/2012/feb/21/coach-tour-m25|title=Coach tour of the M25 – a great day out|first=Patrick|last=Barkham|newspaper=The Guardian|date=21 February 2012|access-date=28 May 2019}}</ref> The interchange with the [[M23 motorway]] near [[Reigate]] is a [[Stack interchange#Four-level stack|four-level stack]]; one of only a few examples in Britain.{{sfn|Hamilton|2015|p=43}} Past this, the M25 runs close to the [[Surrey Hills National Landscape]].<ref name=leadbetter/>
[[File:M23-M25 Intersection - geograph.org.uk - 15455.jpg|thumb|Four level stack interchange at junction 7 with the M23]]
To the west, the M25 passes close to the edge of Heathrow Airport, and within sight of [[Windsor Castle]].<ref>{{cite news|url=https://www.independent.co.uk/travel/uk/trail-of-the-unexpected-the-m25-2088173.html|title=Trail of the unexpected: The M25|newspaper=The Independent|first=Simon|last=Calder|date=25 September 2010|access-date=28 May 2019}}</ref> North of this, it goes under the [[Chalfont Viaduct]] railway bridge, completed in 1906, which carries the [[Chiltern Main Line]]. [[Red kite]]s can often be seen overhead to the north of this, up to junction 21. The northern section of the M25 passes close to [[All Saints Pastoral Centre]] near [[London Colney]], [[Waltham Abbey]] and [[Copped Hall]].<ref name=leadbetter/><ref name=barkham/> This section also features two [[Tunnel#Cut-and-cover|cut-and-cover tunnels]], including the [[Bell Common Tunnel]].<ref name=barkham/> The north-eastern section of the motorway passes close to [[North Ockendon]], the only settlement of Greater London situated outside the M25.<ref name=independent_20161017/> It then runs close to the [[Rainham Marshes Nature Reserve]] before reaching the northern end of the Dartford Crossing.<ref name=leadbetter/>

In 2004, following an opinion poll, the [[London Assembly]] proposed aligning the Greater London boundary with the M25.{{efn|This move would be bound to be resisted by the communities affected, including Watford, [[Loughton]] and [[Epsom]].<ref>{{cite web|url=http://www.london.gov.uk/view_press_release_a.jsp?releaseid=3002|title=Poll says M25 is London's "natural boundary"|work=London Assembly|date=2 March 2004|archive-url=https://web.archive.org/web/20081009152623/http://www.london.gov.uk/view_press_release_a.jsp?releaseid=3002 |archive-date=9 October 2008 }}</ref>}} "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; it states a requirement of "a suitable proportion of the programmes made in the United Kingdom" to be made "in the United Kingdom outside the M25 area", defined in Section 362 as "the area the outer boundary of which is represented by the London Orbital Motorway (M25)".<ref>{{cite web| url=http://www.legislation.gov.uk/ukpga/2003/21 | title=Communications Act 2003 | publisher=The National Archives | year=2003 | access-date=5 September 2011}}</ref><ref>{{cite web|url=https://www.ofcom.org.uk/__data/assets/pdf_file/0017/7073/c4licence.pdf|title=Channel 4 Licence|publisher=[[Ofcom]]|access-date=20 May 2019}}</ref>

Sections of the M25 form part of two long-distance [[International E-road network|E-roads]], designated by the [[United Nations Economic Commission for Europe]]. The [[European route E15|E15]], which runs from [[Inverness]] to [[Algeciras]],{{sfn|United Nations Economic Commission for Europe|2016|p=11}} follows the M25 and A282 clockwise from the A1(M) at junction 23 to the M20 at junction 3;<ref name="AAAtlas"/> while the [[European route E30|E30]] [[Cork (city)|Cork]] to [[Omsk]] route runs from the M4 at junction 15, clockwise to the A12 at junction 28.<ref name="AAAtlas"/> The United Kingdom is formally part of the E-roads network but, unlike in other countries, these routes are not marked on any road signs.<ref>{{cite web |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/2439/roadnetworkconsultation.pdf |author=[[Department for Transport]] |pages=13–14 |title=Road Network Policy Consultation |date=January 2011}}</ref>

===Features===

The M25 was originally built mostly as a dual three-lane motorway.{{sfn|Hamilton|2015|p=25}} Much of this has since 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 [[smart motorway]]s in many others.<ref name=bp/>

Two [[motorway service area]]s are on the M25, and two others are directly accessible from it. Those on the M25 are [[Clacket Lane services|Clacket Lane]] between junctions 5 and 6 (in the south-east) and [[Cobham services|Cobham]] between junctions 9 and 10 (in the south-west). Those directly accessible from it are [[South Mimms services|South Mimms]] off junction 23 (to the north of London) and [[Thurrock services|Thurrock]] off junction 31 (to the east of London).<ref name = cobhamServices>{{Cite web |publisher=[[Highways Agency]] |title=M25 MSA New Barn Farm Cobham |access-date=14 August 2010 |url=http://www.highways.gov.uk/roads/projects/26511.aspx|archive-url=http://webarchive.nationalarchives.gov.uk/20100303165935/http://www.highways.gov.uk/roads/projects/26511.aspx |archive-date=3 March 2010}}</ref><ref name=CobhamOpen>{{cite news |url=https://www.bbc.co.uk/news/uk-england-sussex-19583309 |title=Cobham M25 service station opened |date=13 September 2012 |work=[[BBC News]] |access-date=13 September 2012}}</ref>

As is common with other motorways, the M25 is equipped with emergency ("SOS") telephones. These connect to two [[National Highways]] operated control centres at [[Godstone]] (for junctions 1 to 15 inclusive) and [[South Mimms]] (for 16–31). The Dartford Crossing has a dedicated control centre. There is an extensive network of [[closed-circuit television]] (CCTV) on the motorway so incidents can be easily identified and located. A number of [[four-wheel drive|4×4]] vehicles patrol the motorway, attempting to keep traffic moving where possible, and assisting the local police. They can act as a [[rolling roadblock]] when there are obstacles on the road.{{sfn|Hamilton|2015|p=24}}

When completed, the M25 only had [[street lighting]] for {{convert|65|miles}} of its {{convert|117|miles|adj=on}} length.<ref>{{cite web|url=https://hansard.parliament.uk/commons/1986-02-06/debates/0a2b2f7d-26ea-4c54-90e7-7aa69c07f435/Roads(LightingAndSigns)|title=Roads (Lighting and Signs)|first=Nicholas|last=Ridley|author-link=Nicholas Ridley, Baron Ridley of Liddesdale|work=Hansard|date=6 February 1986|access-date=13 May 2019}}</ref> Originally, [[sodium vapor lamp|low pressure sodium]] (SOX) lighting was the most prominent technology used, but this has been gradually replaced with high-pressure sodium (SON) lighting. {{asof|2015}} the motorway has more than 10,000 streetlights.{{sfn|Hamilton|2015|p=26}} The M25 has a number of pollution control valves along its length, which can shut off drainage in the event of a chemical or fuel spill.{{sfn|Hamilton|2015|p=26}}

==History==

===Plans===
[[File:Ringways 3 & 4.png|thumb|left|Map of Ringways 3 & 4 showing sections combined to form the M25]]

The idea of a general bypass around London was first proposed early in the 20th century. An outer orbital route around the capital had been suggested in 1913, and was re-examined as a motorway route in [[Charles Bressey|Sir Charles Bressey's]] and [[Edwin Lutyens|Sir Edwin Lutyens']] ''The Highway Development Survey, 1937''.{{sfn|Bramley|1946|p=146}} [[Patrick Abercrombie|Sir Patrick Abercrombie's]] ''[[County of London Plan|County of London Plan, 1943]]'' and ''Greater London Plan, 1944'' proposed a series of five roads encircling the capital.{{sfn|Smith|2001|p=148}}<ref>{{cite book|url=https://books.google.com/books?id=sWw9AAAAMAAJ&q=%22county+of+london+plan%22+1943+orbital|title=County of London plan|publisher=London County Council|author=John Henry Forshaw, Sir Patrick Abercrombie|year=1943|page=13}}</ref> The northern sections of the M25 follow a similar route to the [[Outer London Defence Ring]], a concentric series of anti-tank defences and pillboxes designed to slow down a potential German invasion of the capital during [[World War II]].{{sfn|Hamilton|2015|p=19}} This was marked as the D Ring on Abercombie's plans. Following the war, 11 separate [[county council]]s told the [[Ministry of Transport (United Kingdom)|Ministry of Transport]] that an orbital route was "first priority" for London.{{sfn|Asher|2018|p=113}}

Plans stalled because the route was planned to pass through several urban areas, which attracted criticism. The original D Ring through northwest London was intended to be a simple upgrade of streets. In 1951, Middlesex County Council planned a route for the orbital road through the county, passing through [[Eastcote]] and west of [[Bushey]], connecting with the proposed [[M1 motorway]], but it was rejected by the Ministry two years later. An alternative route via [[London Borough of Harrow|Harrow]] and [[Ealing]] was proposed, but this was abandoned after the council revealed the extent of property demolition required.{{sfn|Asher|2018|p=113}}

In 1964, the [[London County Council]] announced the [[London Ringways]] plan, to consist of four concentric motorway rings around London.{{sfn|Asher|2018|p=43,112}} The following year, the transport minister [[Barbara Castle]] announced that the D Ring would be essential to build. The component parts of what became the M25 came from [[London Ringways#Ringway 3|Ringway 3]] / [[M16 motorway]] in the north and [[London Ringways#Ringway 4|Ringway 4]] in the south.{{sfn|Asher|2018|p=113}}

The Ringways plan was controversial owing to the destruction required for the inner two ring roads, ([[London Ringways#Ringway 1|Ringway 1]] and [[London Ringways#Ringway 2|Ringway 2]]). Parts of Ringway 1 were constructed (including the [[West Cross Route]]), despite stiff opposition, before the overall plan was postponed in February 1972. In April 1973, the [[Greater London Council]] elections resulted in a [[Labour Party (UK)|Labour Party]] victory; the party then formally announced the cancellation of the Ringways running inside Greater London.{{sfn|Asher|2018|p=103}} This did not affect the routes that would become the M25, because they were planned as central government projects from the outset.{{sfn|Asher|2018|p=111}}

===Construction===
[[File:M25 - Work In Progress at Tatling End - geograph.org.uk - 37213.jpg|thumb|View north from Higher [[Denham, Buckinghamshire|Denham]] Fire Station at Tatling End on the A40 in July 1984, with the [[Chiltern Main Line]] five-arch 1906 [[Chalfont Viaduct]], originally built to straddle the [[River Misbourne]] ]]
There was no individual [[public inquiry]] into the M25 as a whole.{{sfn|Asher|2018|p=116}} Each section was presented to planning authorities in its own right and was individually justified, with 39 separate public inquiries relating to sections of the route. The need for the ministry to negotiate with local councils meant that more junctions with local traffic were built than originally proposed.{{sfn|Asher|2018|p=117}} A report in 1981 showed that the M25 had the potential to attract office and retail development along its route, negating the proposed traffic improvements and making Central London a less desirable place to work.{{sfn|Asher|2018|p=118}} None of the motorway was prevented from being built by objections at the public inquiries.{{sfn|Hamilton|2015|p=11}} However, as a consequence of the backlash against the Ringways, and criticism at the public inquiries, the motorway was built with environmental concerns in mind. New features included additional earth mounds, cuttings and fences that reduced noise, and over two million trees and shrubs to hide the view of the road.{{sfn|Moran|2009|pp=208–209}}

[[File:Progress on M25 motorway, south of Cobham - geograph.org.uk - 6442228.jpg|thumb|right|South of Cobham in October 1983]]
Construction of parts of the two outer ring roads, Ringways 3 and 4, began in 1973. The first section, between South Mimms and Potters Bar in Hertfordshire (junctions 23 to 24) opened in September 1975.{{sfn|Asher|2018|p=115}}<ref name="tmad">{{cite web|title=M25 : London Orbital Motorway – Dates|url=http://www.ukmotorwayarchive.org.uk/en/motorways/motorway-listing/m25-london-orbital-motorway/dates.cfm|archive-url=https://web.archive.org/web/20200803151154/http://www.ukmotorwayarchive.org.uk/en/motorways/motorway-listing/m25-london-orbital-motorway/dates.cfm|archive-date=3 August 2020|work=UK Motorway Archive}}</ref> It was provisionally known as the M16 and was given the temporary general-purpose road designation [[A1178 road|A1178]].<ref>{{cite news|url=https://www.independent.co.uk/travel/news-and-advice/simon-calder-how-london-got-its-ring-road-2088171.html|title=How London got its Ring Road|first=Simon|last=Calder|newspaper=The Independent|date=25 September 2010|access-date=11 May 2019}}</ref> A section of the North Orbital Road between [[Rickmansworth]] and [[Hunton Bridge]] was proposed in 1966, with detailed planning in 1971. The North Orbital Extension was given the go-ahead in January 1973, from Maple Cross. It was 6.2 miles, and was to cost £6.5m.<ref>''Buckinghamshire Examiner'' Friday 26 January 1973, page 1</ref> The road was constructed to motorway standards and opened on Thursday 26 February 1976, as a section of the [[A405 road|A405]].<ref>''Birmingham Daily Post'' Thursday 26 February 1976, page 25</ref><ref>{{London Gazette | issue = 47053 | date = 28 October 1976 | pages = 14527-14528}}</ref> It eventually became part of the M25's route.{{sfn|Asher|2018|p=115}}<ref name=tmad/> The section to the south, from [[Heathrow Airport]] to Rickmansworth had five separate routes proposed when a public inquiry was launched in 1974. The Department of Transport sent out 15,000 questionnaires about the preferred route, with 5,000 replies. A route was fixed in 1978, with objections delaying the start of construction in 1982.{{sfn|Hamilton|2015|p=11}}

[[File:Progress on M25 motorway, south of Cobham - geograph.org.uk - 6442227.jpg|thumb|right|Construction in October 1983]]
The southern section of what became the M25 through Surrey and Kent was first conceived to be an east–west road south of London to relieve the [[A25 road|A25]], and running parallel to it, with its eastern end following the route of what is now the [[M26 motorway|M26]]. It was originally proposed as an all-purpose route, but was upgraded to motorway standard in 1966. It was the first section of the route announced as M25 from the beginning. The first section from [[Godstone]] to [[Reigate]] (junctions 6 to 8) was first planned in 1966 and opened in February 1976.{{sfn|Asher|2018|p=115}}<ref name=tmad/> A section of Ringway 3 south of the river between Dartford and Swanley (junctions 1 to 3) was constructed between May 1974 and April 1977.<ref name=tmad/>

[[File:Bell Common Tunnel - geograph.org.uk - 53233.jpg|thumb|left|Inside the [[bell Common#Tunnel|Bell Common Tunnel]] near [[Epping, Essex|Epping]]]]
In 1975, following extensive opposition to some parts of Ringway 3 through Middlesex and South London, the transport minister [[John Gilbert, Baron Gilbert|John Gilbert]] announced that the north section of Ringway 3 already planned would be combined with the southern section of Ringway 4, forming a single orbital motorway to be known as the M25, and the M16 designation was dropped. This scheme required two additional sections to join what were two different schemes, from Swanley to Sevenoaks in the south-east and Hunton Bridge to Potters Bar in the north-west. The section of Ringway 3 west of South Mimms anti-clockwise around London to Swanley in Kent was cancelled.{{sfn|Asher|2018|p=116}}

The section from Potters Bar to the [[Dartford Tunnel]] was constructed in stages from June 1979 onwards, with the final section between [[Waltham Cross]] (junction 25) to [[Theydon Garnon]] (junction 27) opening in January 1984.<ref name=tmad/> This section, running through [[Epping Forest]], attracted opposition and protests. In 1973, local residents had parked [[combine harvester]]s in [[Parliament Square]] in protest against the road, draped with large banners reading "Not Epping Likely". As a consequence of this, the [[Bell Common Tunnel]] that runs in this area is twice as long as originally proposed.{{sfn|Asher|2018|p=119}}

The most controversial section of the M25 was that between Swanley and Sevenoaks (junctions 3 to 5) in Kent across the [[Darenth|Darenth Valley]], [[Badgers Mount]] and the [[North Downs]]. An 1,800-member group named Defend Darenth Valley and the North Downs Action Group (DANDAG) argued that the link was unnecessary, it would damage an [[Area of Outstanding Natural Beauty]] and it would be primarily used by local traffic as a bypass for the old [[A21 road (England)|A21 road]] between Farnborough and Sevenoaks.{{sfn|Asher|2018|p=121}} After a length inquiry process, chaired by [[George Dobry]] [[Queen's Counsel|QC]], the transport minister [[Kenneth Clarke]] announced the motorway would be built as proposed.{{sfn|Asher|2018|p=120}}

The section from the [[M40 motorway]] to the 1970s North Orbital Road construction (junctions 16 to 17) opened in January 1985.{{sfn|Asher|2018|p=121}} The route under the [[Chalfont Viaduct]] meant the motorway was restricted to a width of three lanes in each direction.<ref>{{cite news|url=https://www.telegraph.co.uk/travel/destinations/europe/united-kingdom/galleries/M25-The-best-of-Britains-most-hated-motorway/m25-summary/ |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/travel/destinations/europe/united-kingdom/galleries/M25-The-best-of-Britains-most-hated-motorway/m25-summary/ |archive-date=12 January 2022 |url-access=subscription |url-status=live|title=M25: The best of Britain's most hated motorway|newspaper=The Daily Telegraph|access-date=11 May 2019}}{{cbignore}}</ref>

The [[Prime Minister of the United Kingdom|Prime Minister]], [[Margaret Thatcher]], officially opened the M25 on 29 October 1986, with a ceremony in the section between junctions 22 to 23 ([[London Colney]] and [[South Mimms]]).<ref name=independent_20161017>{{cite news|url=https://www.independent.co.uk/life-style/motoring/features/the-m25-were-on-the-road-to-nowhere-420365.html|title=The M25 : We're on the road to nowhere|newspaper=The Independent|date=17 October 2006|access-date=11 May 2019}}</ref> To avoid the threat of road protesters, the ceremony was held a quarter of a mile from the nearest bridge.{{sfn|Moran|2009|p=209}} The total estimated cost of the motorway was around £1{{nbsp}}billion. It required {{convert|2|e6tonne|e6ST|abbr=off}} of concrete, {{convert|2.5|e6tonne|e6ST|abbr=off}} of [[Asphalt concrete|asphalt]] and involved the removal of {{convert|49|e6m3|e6cuft|abbr=off}} of spoil. Upon completion, it was the longest orbital motorway in the world at {{convert|117|miles}}.{{sfn|Asher|2018|p=121}}{{efn|name=Berliner_Ring_is_longer}} At the opening ceremony, Thatcher announced that {{convert|98|mi}} had been constructed while the [[Conservative Party (UK)|Conservative Party]] were in office, calling it "a splendid achievement for Britain".{{sfn|Moran|2009|p=209}} A 58-page brochure was published, commemorating the completion of the motorway.{{sfn|Hamilton|2015|p=14}}

===Operational history===
[[File:M4 M25 junction.jpg|thumb|The M4/M25 motorway junction (junction 15), near [[Heathrow Airport]]]]

The M25 was initially popular with the public. In the [[1987 United Kingdom general election|1987 general election]], the [[Conservative Party (UK)|Conservatives]] won in every constituency that the motorway passed through, in particular gaining [[Thurrock (UK Parliament constituency)|Thurrock]] from [[Labour Party (UK)|Labour]]. Coach tours were organised for a trip around the new road. However, it quickly became apparent that the M25 suffered from chronic congestion. A report in ''[[The Economist]]'' said it "had taken 70 years to plan [the motorway], 12 to build it and just one to find it was inadequate". Thatcher rebuked the negative response, calling it "carping and criticism".{{sfn|Asher|2018|p=122}}

Traffic levels quickly exceeded the maximum design capacity. Two months before it opened, the government admitted that the three-lane section between junctions 11 and 13 was inadequate and that it would have to be widened to four.{{sfn|Asher|2018|p=122}} In 1990, the [[Secretary of State for Transport]] announced plans to widen the whole of the M25 to four lanes.<ref>{{Cite web|url=https://api.parliament.uk/historic-hansard/written-answers/1990/dec/03/m25|title=M25 (Hansard, 3 December 1990)|website=UK Parliament|date=3 December 1990|access-date=19 July 2019}}</ref> By 1993 the motorway, designed for a maximum of 88,000 vehicles per day, was carrying 200,000.<ref>{{Cite news|url=https://www.independent.co.uk/news/uk/the-bluffers-briefing-on-the-m25-1499570.html|title=The bluffer's briefing on: The M25 | work=The Independent | location=London | date=24 March 1993 | access-date=12 May 2010}}</ref> At that time, the M25 carried 15% of UK motorway traffic and there were plans to add six lanes to the section from junctions 12 to 15, as well as widening the rest of the motorway to four lanes.<ref>{{Cite web|url=https://api.parliament.uk/historic-hansard/commons/1993/feb/18/m25-widening|title=M25 (Widening)|work=[[Hansard|Parliamentary Debates (Hansard)]]|date=18 February 1993|access-date=19 July 2019}}</ref>

In parts, particularly the western third, that plan went ahead. Again, however, plans to widen further sections to eight lanes (four each way) were scaled back in 2009 in response to rising costs. The plans were reinstated in the agreed [[Highways Agency]] 2013–14 business plan.<ref>{{Cite news|url=http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6571879.ece|archive-url=https://web.archive.org/web/20090709142710/http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6571879.ece|url-status=dead|archive-date=9 July 2009|title=Rising costs put the brakes on dozens of roadbuilding projects | newspaper=The Times | location=London | first=Ben | last=Webster | date=25 June 2009 | access-date=12 May 2010}}</ref>

In June 1992, the [[Department for Transport]] (DfT) announced a proposal to widen the section close to Heathrow Airport to fourteen lanes by way of three additional link roads.{{sfn|Asher|2018|p=126}} That attracted fierce opposition from [[Road protest in the United Kingdom|anti-motorway protesters]] who were critical of the [[Newbury Bypass]] and other schemes,<ref>{{Cite news|url=https://www.independent.co.uk/news/uk/the-roadblock-that-became-a-bandwagon-1614137.html|title=The roadblock that became a bandwagon|work=The Independent | location=London | first=Christian | last=Wolmar | date=4 April 1995 | access-date=12 May 2010}}</ref> but also from local authorities. Surrey County Council led a formal objection to the widening scheme,{{sfn|Asher|2018|p=126}} and it was cancelled shortly afterwards.<ref>{{Cite news|url=https://www.independent.co.uk/opinion/pointless-lies-that-reveal-so-much-1613955.html|title=Pointless lies that reveal so much |newspaper=The Independent | location=London | first=Nick | last=Cohen | date=2 April 1995 | access-date=12 May 2010}}</ref> In 1994, the Standing Advisory Committee on Trunk Road Appraisal published a report saying that "the M25 experience most probably does ... serve as an example of a case where roads generate traffic" and that further improvements to the motorway were counter-productive.{{sfn|Asher|2018|p=126}} In April 1995, the Transport Minister [[Brian Mawhinney]] announced that the Heathrow link roads would be scrapped.{{sfn|Asher|2018|p=127}}

[[File:M25 motorway 2004-04-25.jpg|thumb|left|The M25 motorway near Heathrow, showing a [[Motorway Incident Detection and Automatic Signalling|MIDAS]] installed gantry]]

In 1995, a contract was awarded to widen the section between junctions 8 and 10 from six to eight lanes at a cost of £93.4{{nbsp}}million,<ref>{{Cite news|url=http://www.cnplus.co.uk/news/m25-scoop-for-balfour-in-surrey/955396.article|title=M25 scoop for Balfour in Surrey|publisher=Construction News|access-date=12 May 2019}}</ref> and a [[Motorway Incident Detection and Automatic Signalling]] (MIDAS) system was introduced from junction 10 to junction 15 in 1995, at a cost of £13.5M. That was extended to junction 16 in 2002, at a cost of £11.7M. The system consists of a distributed network of traffic and weather sensors, [[speed camera]]s and [[Speed limit#Variable speed limits|variable-speed signs]], that control traffic speeds with little human supervision. It has improved traffic flow slightly, reducing the amount of start-stop driving.<ref>{{Cite web|url=http://www.dft.gov.uk/itstoolkit/CaseStudies/m25-controlled-motorway.htm|title=Case Study – M25 Controlled Motorway|work=Highways Agency|url-status=dead|archive-url=https://web.archive.org/web/20120926095159/http://www.dft.gov.uk/itstoolkit/CaseStudies/m25-controlled-motorway.htm |archive-date=26 September 2012}}</ref>

After Labour won the [[1997 United Kingdom general election|1997 election]], the road budget was cut from £6{{nbsp}}billion to £1.4{{nbsp}}billion.{{sfn|Asher|2018|p=127}} However, the DfT announced new proposals to widen the section between junction 12 (M3) and junction 15 (M4) to 12 lanes. At the [[Heathrow Terminal 5]] public inquiry, a Highways Agency official said that the widening was needed to accommodate traffic to the proposed new terminal, but the transport minister said that no such evidence had been given.<ref>{{Cite news|url=https://www.independent.co.uk/news/minister-gives-green-light-to-widen-m25-1274054.html|title=Minister gives green light to widen M25|work=The Independent | location=London | first=Christian | last=Wolmar | date=21 March 1997 | access-date=12 May 2010}}</ref> Environmental groups objected to the decision to go ahead with a scheme to create the widest motorways in the UK, without holding a [[public inquiry]].<ref>{{Cite web|url=http://www.getsurrey.co.uk/news/s/80175_plans_to_widen_m25_to_12_lanes_under_attack |title=Plans to widen M25 to 12 lanes under attack | work = Get Surrey | url-status=dead |archive-url=https://web.archive.org/web/20130614224728/http://www.getsurrey.co.uk/news/s/80175_plans_to_widen_m25_to_12_lanes_under_attack |archive-date=14 June 2013 |access-date=12 August 2020}}</ref> [[Friends of the Earth]] claimed the real reason for the widening was to support Terminal 5.{{sfn|Asher|2018|p=127}} The decision was again deferred. A ten-lane scheme was announced in 1998,<ref>{{Cite magazine|url=https://www.newcivilengineer.com/archive/baa-makes-plans-for-terminal-5-despite-inquiry-06-08-1998/|title=BAA makes plans for Terminal 5 despite inquiry|magazine=New Civil Engineer|date=6 August 1998}}</ref> and the £148{{nbsp}}million 'M25 Jct 12 to 15 Widening' contract was awarded to [[Balfour Beatty]] in 2003.<ref>{{cite web|url=http://www.bbcel.co.uk/capabilities/roads/62_m25-junctions-12-15-widening |title=M25 Junctions 12 – 15 Widening |quote=In 2003, Balfour Beatty Civil Engineering was awarded the £148 million contract to widen the 10-mile stretch of the M25, between Junction 12 (the M3 Interchange) and Junction 15 (the M4 Interchange). |url-status=dead |archive-url=https://web.archive.org/web/20120317091615/http://www.bbcel.co.uk/capabilities/roads/62_m25-junctions-12-15-widening |archive-date= 17 March 2012 }}</ref> The scheme was completed in 2005, with dual-five lanes between junctions 12 and 14 and dual-six lanes from junctions 14 to 15.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/4084.aspx|title=M25 Jct 12 to 15 Widening|work=Highways Agency|archive-url=http://webarchive.nationalarchives.gov.uk/20080926001640/http://www.highways.gov.uk/roads/projects/4084.aspx|archive-date=26 September 2008}}</ref>

In 2007, junction 25 (A10/Waltham Cross) was remodelled to increase capacity. The nearby Holmesdale Tunnel was widened to three lanes in an easterly direction, and an additional left-turn lane added from the A10 onto the motorway. The total cost was £75{{nbsp}}million.<ref>{{Cite web|url=http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=132377|title=£75 Million Refurbishment for M25 Holmesdale Tunnel and Junction 25 Improvement work starts on Saturday 6 May |work=Highways Agency |archive-url=http://webarchive.nationalarchives.gov.uk/20081106072611/http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=132377 |archive-date=6 November 2008}}</ref><ref>{{cite web|url=https://highwaysengland.citizenspace.com/he/m25-junction-25-improvement-scheme/ |title=M25 Junction 25 Improvement |work=Highways England |access-date=13 May 2019}}</ref>

Work to widen the exit slip-roads in both directions at junction 28 ([[A12 road (England)|A12]] / A1023) was completed in 2008. That was designed to reduce the amount of traffic queuing on the slip roads at busy periods, particularly traffic from the clockwise M25 joining the northbound A12.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/3520.aspx|title=M25 Junction 28 / A12 / Brook Street Interchange|work=Highways Agency|archive-url=http://webarchive.nationalarchives.gov.uk/20080926001943/http://www.highways.gov.uk/roads/projects/3520.aspx|archive-date=26 September 2008}}</ref> In 2018, a new scheme was proposed, because the junction had reached capacity, accommodating over 7,500 vehicles per hour. The scheme involved building a two-lane link road between the M25 and the A12. The work was expected to be completed around 2021/22.<ref>{{cite news|url=https://www.eadt.co.uk/business/final-consultation-on-scheme-for-a12-m25-brentwood-junction-1-5806376|title=A12 junction to get major overhaul|newspaper=East Anglian Daily Times|date=5 December 2018|access-date=13 May 2019}}</ref>

===Widening===
[[File:Widening of the M25 Motorway near South Mimms.jpg|thumb|Widening of the M25 Motorway near South Mimms]]

In 2006, the Highways Agency proposed widening {{convert|63|mi|km}} of the M25 from six to eight lanes, between junctions 5 and 6, and 16 to 30, as part of a Design, Build, Finance and Operate (DBFO) project.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/7717.aspx|title=Prequalification Document|work=Highways Agency|access-date=20 January 2008|archive-url=http://webarchive.nationalarchives.gov.uk/20081107095325/http://www.highways.gov.uk/roads/7717.aspx|archive-date=7 November 2008}}</ref> A shortlist of contractors was announced in October 2006 for the project, which was expected to cost £4.5{{nbsp}}billion.<ref>{{Cite web |url=http://www.contractjournal.com/Articles/2006/10/13/52504/highways-agency-announces-shortlist-for-4.5bn-m25-dbfo.html |title=Highways Agency announces shortlist for £4.5bn M25 DBFO |publisher=Contract Journal |access-date=20 January 2008 |archive-date=16 January 2016 |archive-url=https://web.archive.org/web/20160116183257/http://www.contractjournal.com/Articles/2006/10/13/52504/highways-agency-announces-shortlist-for-4.5bn-m25-dbfo.html |url-status=dead }}</ref> Contractors were asked to resubmit their bids in January 2008,<ref>{{Cite web|url=https://www.constructionnews.co.uk/archive/highways-agency-calls-for-m25-widening-bids-to-be-resubmitted-16-01-2008/ |title=Highways Agency calls for M25 widening bids to be resubmitted |publisher=Construction Journal |date=16 January 2008 |author=Andrea Klettner |access-date=20 January 2008 |url-status=live |archive-url=https://web.archive.org/web/20200812103507/https://www.constructionnews.co.uk/archive/highways-agency-calls-for-m25-widening-bids-to-be-resubmitted-16-01-2008/ |archive-date=12 August 2020}}</ref> and in June 2009 the new transport minister indicated that the cost had risen to £5.5{{nbsp}}billion and the benefit to cost ratio had dropped considerably.<ref>{{Cite magazine|url=https://www.newcivilengineer.com/latest/cost-escalation-hits-m25-widening-benefit-to-cost-ratios-16-06-2009/|title=Cost escalation hits M25 widening benefit to cost ratios|magazine=New Civil Engineer|date=16 June 2009}}</ref> In January 2009 the government announced that plans to widen the sections from junctions 5 to 7 and 23 to 27 had been 'scrapped' and that hard shoulder running would be introduced instead. However, widening to four lanes was reinstated in the 2013–14 Highways Agency Business Plan.<ref name=bp>{{cite web|url=http://assets.highways.gov.uk/about-us/corporate-documents-business-plans/S120450_Highways_Agency_Business_Plan_2013-14.pdf |title=Business Plan 2013–14 |url-status=dead|archive-url=https://web.archive.org/web/20130515101239/http://assets.highways.gov.uk/about-us/corporate-documents-business-plans/S120450_Highways_Agency_Business_Plan_2013-14.pdf |archive-date=15 May 2013 |work=Highways Agency}}</ref><ref>{{Cite news|url=https://www.theguardian.com/politics/2009/jan/18/motorways-geoff-hoon|title=Ministers scrap plan to widen motorways | newspaper=The Guardian | location=London | first=Toby | last=Helm | date=18 January 2009 | access-date=12 May 2010}}</ref>

In 2009, a £6.2{{nbsp}}billion M25 DBFO [[private finance initiative]] contract<ref>{{Cite news|url=http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6322870.ece|archive-url=https://web.archive.org/web/20110612191248/http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6322870.ece|url-status=dead|archive-date=12 June 2011|title=PFI deal for M25 agreed despite price rise | newspaper=The Times | location=London | first=Ben | last=Webster | date=20 May 2009 | access-date=12 May 2010}}</ref> was awarded to Connect Plus to widen the sections between junctions 16 to 23 and 27 to 30, and maintain the M25 and the Dartford Crossing for a 30-year period.<ref>{{Cite web|url=http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=174136|title=£6.2 billion M25 Design, Build, Finance and Operate (DBFO) contract awarded|work=Highways Agency|archive-url=http://webarchive.nationalarchives.gov.uk/20091115022317/http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=174136|archive-date=15 November 2009}}</ref>

Work to widen the section between junctions 16 (M40) and 23 (A1(M)) to dual four lanes<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/5747.aspx |title=M25 Jct 16 to 23 Widening |work=Highways Agency|url-status=dead |archive-url=https://web.archive.org/web/20120910043422/http://www.highways.gov.uk/roads/projects/5747.aspx |archive-date=10 September 2012 }}</ref> started in July 2009 at an estimated cost of £580{{nbsp}}million.<ref>{{Cite news|url=http://news.bbc.co.uk/1/hi/england/8139940.stm|title=M25 widening to four lanes begins|work=BBC News | date=8 July 2009 | access-date=12 May 2010}}</ref> The junction 16 to 21 (M1) section was completed by July 2011 and the junction 21 to 23 by June 2012.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/13825.aspx|title=Highways Agency Timetable|archive-url=http://webarchive.nationalarchives.gov.uk/20080926033144/http://www.highways.gov.uk/roads/projects/13825.aspx|archive-date=26 September 2008}}</ref> Works to widen the junctions 27 (M11) to 30 (A13) section to dual four lanes also started in July 2009. The junction 27 to 28 (A12) section was completed in July 2010,<ref>{{Cite web|url=http://www.fleetdirectory.co.uk/fleet-news/index.php/2009/09/30/weekly-summary-of-roadworks-in-m25-sphere-30092009/|title=Weekly Summary of Roadworks in M25 Sphere – 30 September 2009|work=Fleet Directory|access-date=11 October 2009|archive-url=https://web.archive.org/web/20091002035548/http://www.fleetdirectory.co.uk/fleet-news/index.php/2009/09/30/weekly-summary-of-roadworks-in-m25-sphere-30092009/|archive-date=2 October 2009|url-status=dead}}</ref> and the junction 28 to 29 (A127) in June 2011, and finally the junction 29 to 30 (A13) section opened in May 2012.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/5739.aspx |title=M25 Jct 27 to 30 Widening |work=Highways Agency |url-status=dead |archive-url=https://web.archive.org/web/20120329130227/http://www.highways.gov.uk/roads/projects/5739.aspx |archive-date= 29 March 2012 }}</ref>

Work to introduce smart motorway technology and permanent [[Shoulder (road)|hard shoulder running]] on two sections of the M25 began in 2013. The first section between junctions 5 (A21/M26) and 7 (M23) started construction in May 2013 with the scheme being completed and opened in April 2014.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/5735.aspx|title=M25 Junctions 5 to 7 Managed Motorways|work=Highway Agency|access-date=11 October 2009|archive-url=https://web.archive.org/web/20120908034609/http://www.highways.gov.uk/roads/projects/5735.aspx|archive-date=8 September 2012|url-status=dead}}</ref> The second section, between junctions 23 (A1/A1(M)) and 27 (M11), began construction in February 2013 and was completed and opened in November 2014.<ref>{{Cite web|url=http://www.highways.gov.uk/roads/projects/5743.aspx|title=M25 Junctions 23 to 27 Managed Motorways|work=Highways Agency|access-date=10 December 2008|archive-url=https://web.archive.org/web/20120817142908/http://www.highways.gov.uk/roads/projects/5743.aspx|archive-date=17 August 2012|url-status=dead}}</ref>

In December 2016, Highways England completed the capacity project at junction 30 (Thurrock) as part of the [[Thames Gateway]] Delivery Plan.<ref>{{cite web|url=http://roads.highways.gov.uk/projects/m25-junction-30a13-corridor-relieving-congestion-scheme/|archive-url=https://web.archive.org/web/20170910054525/http://roads.highways.gov.uk/projects/m25-junction-30a13-corridor-relieving-congestion-scheme/|url-status=dead|archive-date=10 September 2017|title=M25 Junction 30 A13 corridor relieving congestion scheme|date=10 September 2017|work=Highways England}}</ref> The £100{{nbsp}}million scheme included widening the M25 to four lanes, adding additional link roads, and improvements to drainage.<ref>{{cite web|url=https://www.highwaysindustry.com/m25-junction-officially-open-after-100million-upgrade/|title=M25 junction officially open after £100million upgrade|work=Highways Industry|date=2 December 2016|access-date=12 May 2019}}</ref>

Work began to widen the M25 and A3 around junction 10 in November 2022.<ref>{{cite news| url  = https://www.getsurrey.co.uk/news/surrey-news/m25-a3-wisley-interchange-looks-30194375 |title=M25 and A3 Wisley interchange looks unrecognisable in video showing new bridge works|work=Get Surrey|date=21 October 2024|accessdate=25 October 2024}}</ref><ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-surrey-65327256 | title = M25: Thousands of trees replanted after widening work | date = 21 April 2023 | work = BBC News|access-date=25 October 2024}}</ref> The project is intended to limit congestion at the junction and allow traffic to proceed more safely.<ref>{{cite web|url=https://nationalhighways.co.uk/our-roads/m25-junction-10-project-profile/|title=M25 junction 10 project profile|date=15 May 2024 |publisher=National Highways|access-date=27 October 2024}}</ref> However, these plans caused concerns about the amount of woodland that would be required.<ref>{{Cite web|last=Fleming|first=Eleanor|date=18 August 2020|title=RHS Wisley's 'last chance' to save 'irreplaceable' trees from M25-A3 scheme | url = https://www.getsurrey.co.uk/news/surrey-news/rhs-wisley-highways-england-plans-18786153|access-date=18 August 2020|website=SurreyLive}}</ref>

In March 2024, National Highways announced the first all-day closure of the M25 in its operational history. The motorway was closed between junctions 10 and 11 from 15–18 March in order to remove a bridleway bridge.<ref>{{cite web|url=https://nationalhighways.co.uk/article/m25-braced-for-first-ever-planned-full-closure-as-drivers-warned-of-long-delays-and-told-to-only-travel-if-necessary/|title=M25 braced for first ever planned full closure as drivers warned of long delays and told to only travel if necessary|work=National Highways|date=5 March 2024|accessdate=6 March 2024}}</ref><ref>{{cite news|url=https://www.bbc.co.uk/news/business-68482948|title=M25 section to close for entire weekend|work=BBC News|date=6 March 2024|accessdate=6 March 2024}}</ref> The road was closed completely for two other occasions that year, with a final two closures scheduled for 2025.<ref>{{cite news|url=https://www.bbc.co.uk/news/articles/c0jq5p7nyn1o|title=No more M25 weekend closures in 2024|work=BBC News|date=18 July 2024|access-date=27 October 2024}}</ref>

==Traffic==

[[File:M25 Motorway Clockwise. Approaching Junction 14 For A3113 For Heathrow - geograph.org.uk - 1280493.jpg|thumb|Near [[Heathrow Airport]], the M25 is six lanes wide in each direction.]]

The M25 is one of Europe's busiest motorways. In 2003, a maximum of 196,000 vehicles a day were recorded just south of Heathrow, between junctions 13 and 14.<ref name="Motorway traffic up 4% on 2003">{{cite news|url=http://news.bbc.co.uk/2/hi/uk_news/3558822.stm|title=Motorway traffic up 4% on 2003|access-date=3 January 2009|date=12 August 2004|work=[[BBC News]]}}</ref> The stretch between the nearby junctions 14 and 15 consistently records the highest daily traffic counts on the British strategic road network, with the average flow in 2018 being 219,492 vehicles (lower than the record peak measured in 2014 of 262,842).<ref name="GB Road Traffic Counts">{{Cite web|url=https://data.gov.uk/dataset/208c0e7b-353f-4e2d-8b7a-1a7118467acc/gb-road-traffic-counts|title=GB Road Traffic Counts|date=29 May 2019|website=data.gov.uk|access-date=19 July 2019|archive-url=https://web.archive.org/web/20191001163113/https://data.gov.uk/dataset/208c0e7b-353f-4e2d-8b7a-1a7118467acc/gb-road-traffic-counts|archive-date=1 October 2019|url-status=dead}}</ref>

[[File:Highways Agency Smart Motorways control centre.jpg|thumb|left|A control room for the M25 junction 5–7 [[smart motorway]] scheme]]

Traffic on the M25 is monitored by Connect Plus Services on behalf of National Highways. The company operates a series of transportable CCTV cameras that can be easily moved into congestion hotspots, allowing operators to have a clear view of the motorway and so assess what might be done to tackle particular areas of congestion.<ref>{{cite web|url=https://www.wcctv.co.uk/case-studies/connect-plus-m25-traffic-management-/ |title=Connect Plus M25 Traffic Management |publisher=WCCTV |access-date=14 May 2019}}</ref> Prior to its liquidation in 2018, [[Carillion]] was subcontracted to manage traffic on the M25, delivering live alerts from body-worn cameras via 3G, 4G and Wi-Fi.<ref>{{cite web|url=https://www.wcctv.co.uk/case-studies/carillion-traffic-management-body-worn-cameras/|title=Carillion Traffic Management – Body Worn Cameras|work=WCCTV|access-date=14 May 2019}}</ref>

Since 1995, sections of the M25 have been equipped with variable speed limits, which slow traffic in the event of congestion or an obstruction, and help manage the traffic flow.<ref>{{cite web|url=https://www.legislation.gov.uk/uksi/1995/1094/body/made|title=The M25 Motorway (Junctions 10 to 15) (Variable Speed Limits) Regulations 1995|work=UK Statutory Instruments|date=15 May 1995|access-date=30 September 2022}}</ref> The scheme was originally trialled between junctions 10 and 16, and was made a permanent fixture in 1997.<ref>{{cite report |url=http://www.nao.org.uk/publications/nao_reports/04-05/040515.pdf |title=Report (HC 15, 2004–05): Tackling congestion by making better use of England's motorways and trunk roads (Full Report) |publisher=[[National Audit Office (United Kingdom) |National Audit Office]] |date=26 November 2004 |access-date=17 September 2009 |page=21 |archive-date=11 March 2005 |archive-url=https://web.archive.org/web/20050311035332/http://www.nao.org.uk/publications/nao_reports/04-05/040515.pdf |url-status=dead }}</ref>

The Dartford Crossing is the only fixed vehicle crossing of the Thames east of Greater London.<ref>{{cite news|url=http://www.kentonline.co.uk/dartford/news/dartford-crossing-gantries-17162/|title=Dartford Crossing to get tunnel and bridge closures as Dart Charge introduced and gantries installed near QEII bridge|first=Thom|last=Morris|work=Kent Messenger|date=14 May 2014|access-date=2 July 2014}}</ref> It is also the busiest crossing in the United Kingdom, and consequently puts pressure on M25 traffic.<ref>{{cite news|url=https://www.independent.co.uk/news/uk/home-news/dartfordthurrock-river-crossing-toll-charges-to-rise-7778496.html|title=Dartford-Thurrock River Crossing toll charges to rise|first=Peter|last=Woodman|work=The Independent|date=22 May 2012|access-date=13 July 2014}}</ref> Users of the crossing do not pay a toll, but rather a congestion charge. The signs at the crossing are the same as those deployed over the [[London congestion charge]] zone.<ref>{{cite web|url=https://tfl.gov.uk/modes/driving/congestion-charge/dart-charge|title=Dart Charge|publisher=Transport for London|access-date=14 May 2019}}</ref>

In 2009, the Department for Transport published options for a new [[Lower Thames Crossing]] to add capacity to the Dartford Crossing, or create a new road and crossing linking to the M2 and M20 motorways.<ref>{{Cite web |url=http://www.dft.gov.uk/about/strategy/capacityrequirements/dartfordrivercrossing/chap1execsummary.pdf |title=Dartford River Crossing Study into Capacity Requirement |publisher=Department for Transport |date=20 April 2009 |access-date=26 April 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091203202454/http://www.dft.gov.uk/about/strategy/capacityrequirements/dartfordrivercrossing/chap1execsummary.pdf |archive-date=3 December 2009 }}</ref> Plans for that stalled, and were cancelled in 2013 by the Mayor of London, [[Boris Johnson]], being replaced by a proposed [[Gallions Reach Crossing]]. Initially seen as a straight ferry replacement for the [[Woolwich Ferry]], it was later mooted as a bridge or tunnel.<ref>{{cite news|url=https://www.telegraph.co.uk/news/uknews/road-and-rail-transport/9009627/London-to-get-new-road-tunnel-under-River-Thames-within-decade-promises-Boris-Johnson.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/uknews/road-and-rail-transport/9009627/London-to-get-new-road-tunnel-under-River-Thames-within-decade-promises-Boris-Johnson.html |archive-date=12 January 2022 |url-access=subscription |url-status=live|title=London to get new road tunnel under River Thames within decade, promises Boris Johnson|newspaper=[[Daily Telegraph]]|date=12 January 2012|access-date=26 June 2013}}{{cbignore}}</ref><ref>{{cite news|url=https://www.standard.co.uk/comment/comment/andrew-adonis-boris-cant-put-off-a-new-thames-crossing-in-the-east-8653336.html|title=Boris can't put off a new Thames crossing in the east|author=[[Andrew Adonis, Baron Adonis|Andrew Adonis]]|newspaper=[[London Evening Standard]]|date=11 June 2013|access-date=26 June 2013}}</ref> By 2019, the plans had changed, with the [[Docklands Light Railway]] to be extended to [[Thamesmead]] instead.<ref>{{cite news|url=https://www.newsshopper.co.uk/news/17594843.greenwich-council-reaffirm-backing-dlr-extension-thamesmead/|title=Greenwich Council reaffirm backing of DLR extension to Thamesmead|work=News Shopper|date=24 April 2019|accessdate=6 December 2021}}</ref>

==Incidents==

On 11 December 1984, nine people died and ten were injured in a multiple-vehicle collision between junctions 5 and 6. Twenty-six vehicles were involved when dense fog descended suddenly.<ref>{{Cite web|url=http://www.open.ac.uk/Arts/history-from-police-archives/RB1/Pt4/pt4M25Rta84.html|title=Surrey Constabulary: Part 4: A Policing Revolution: 1976–1992|work=Open University|access-date=27 October 2019|archive-date=3 August 2020|archive-url=https://web.archive.org/web/20200803163308/http://www.open.ac.uk/Arts/history-from-police-archives/RB1/Pt4/pt4M25Rta84.html|url-status=dead}}</ref>

On 16 December 1988, several vehicles were stolen and used as getaway for acts of murder and robbery, using the M25 to quickly move between targets. The [[M25 Three]], including [[Raphael Rowe]], were tried and sentenced to life imprisonment in 1990. Their convictions were overturned in 2000 and Rowe, who studied journalism while in prison, became an [[investigative journalism|investigative journalist]] for the BBC.<ref>{{cite web |url=http://news.bbc.co.uk/1/hi/uk/837275.stm |title=Appeal court frees 'M25 Three' |date=17 July 2000 |website=BBC News |access-date=2 September 2021}}</ref><ref>{{cite web |url=https://www.bbc.co.uk/programmes/profiles/1b2wc5XNwYYfZf2D8LdBxtW/raphael-rowe |title=BBC One – Panorama – Raphael Rowe |website=BBC |access-date=2 September 2021}}</ref>{{sfn|Hamilton|2015|p=15}}

In 1996, [[Kenneth Noye]] murdered Stephen Cameron in a [[road rage]] incident while stopped at traffic lights on an M25 junction in Kent. He was convicted in 2000 and sentenced to life imprisonment.<ref>{{cite news|url=https://www.independent.co.uk/news/uk/crime/kenneth-noye-m25-killer-moved-to-open-prison-murderer-police-stephen-cameron-brinks-matt-hatton-a7882371.html|title=Kenneth Noye: Notorious M25 killer to be moved to open prison|newspaper=The Independent|date=8 August 2017|access-date=22 May 2019}}</ref> He was released in June 2019.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-kent-48367089|title=M25 killer Kenneth Noye to be freed from prison|work=BBC News|date=22 May 2019|access-date=22 May 2019}}</ref><ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-kent-48542576|title=M25 killer Kenneth Noye released from prison|work=BBC News|date=6 June 2019|access-date=19 July 2019}}</ref>

In November 2014, during overnight roadworks, a {{convert|16|ft|adj=on}} piece of road surface near junction 9 at [[Leatherhead]] failed to set correctly due to rain. This created a {{convert|1|ft|adj=on}} pothole in the road and caused a {{convert|12|mile|km|adj=on}} tailback. The Minister for Transport [[John Hayes (British politician)|John Hayes]] criticised the work and the resulting traffic problems.{{sfn|Hamilton|2015|p=27}}

The M25 has had problems with animals and birds on the carriageway. In 2009, the Highways Agency reported that they had been called out several times a week to remove a swan from the motorway around junction 13.{{sfn|Moran|2009|p=145}} There have been several crashes resulting in horses escaping their horseboxes onto the carriageway.<ref>{{cite news|url=https://www.standard.co.uk/news/crime/horses-break-loose-on-motorway-after-horsebox-crash-on-m25-a2328066.html|title=Horses break loose on motorway after horsebox crash on M25|newspaper=London Evening Standard|date=8 August 2015|access-date=19 July 2019}}</ref><ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-surrey-33837350|title=Horses break free in Surrey M25 crash|work=BBC News|date=8 August 2015|access-date=19 July 2019}}</ref><ref>{{cite news|url=https://www.kentlive.news/news/kent-news/horse-involved-crash-m25-led-1787894|title=A horse involved in a crash on the M25 was led to safety|work=Kent Live|date=15 July 2018|access-date=19 July 2019}}</ref>

===Racing===
The motorway has attracted unofficial, and illegal, [[Auto racing|motor racing]]. At the end of the 1980s, before the advent of automated speed enforcement devices, owners of [[supercars]] would meet at night at service stations such as [[South Mimms services|South Mimms]] and conduct time trials.{{sfn|Moran|2009|p=163}} Times below 1 hour were achieved – an average speed of over 117&nbsp;mph (188&nbsp;km/h), which included coming to a halt at the [[Dartford Tunnel]] road user charge payment booths.<ref>{{Cite web| last = May | first = James| author-link = James May | title = Speed, Greed And The M25| publisher = [[BBC Radio 4]] | date = 20 October 2007| url = http://www.bbc.co.uk/radio4/factual/pip/ap895/?focuswin}}
</ref><ref>{{cite press release | title = Programme Information – Network Radio Week 43 | publisher = [[BBC]] Press Office |url=http://www.bbc.co.uk/pressoffice/proginfo/radio/wk43/sat.shtml}}</ref> The winner received champagne rather than money. The ''Enfield Gazette'' referred to an "M25 club", and posters appeared near the M25 advertising the "First London Cannonball Run".{{sfn|Moran|2009|p=163}} The racing had mostly disappeared by the end of the 1980s after speed cameras were introduced.{{sfn|Moran|2009|p=164}}

===Insulate Britain protests===
{{main|Insulate Britain protests}}
In 2021, several sections of the M25 were disrupted after the home energy and insulation campaign group [[Insulate Britain]] blocked junctions including Nos.&nbsp;3 ([[Swanley]]), 6 ([[Godstone]]), 14 (Heathrow), 20 ([[Kings Langley]]) and 31 ([[Lakeside Shopping Centre|Lakeside]]). A spokesman for [[the AA]] said the actions were counterproductive, as they would cause increased vehicle emissions owing to delays, as well having a negative effect on the economy.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-58543603|title=M25 junctions blocked by Insulate Britain campaigners|work=BBC News|date=13 September 2021|access-date=13 September 2021}}</ref><ref>{{cite news|url=https://www.theguardian.com/environment/2021/sep/13/climate-protesters-arrested-after-blocking-m25-junctions-in-rush-hour|title=Climate protesters arrested after blocking M25 junctions in rush hour|newspaper=The Guardian|date=13 September 2021|access-date=13 September 2021}}</ref> 92 people were arrested following the first incident on 13 September, followed by a further 70 two days later. Insulate Britain said they would continue to disrupt the M25 until the government responded.<ref>{{cite news|url=https://www.theguardian.com/environment/2021/sep/15/green-protesters-bring-m25-traffic-to-a-halt-for-second-time-this-week|title=Dozens arrested after protests bring M25 traffic to a halt again|newspaper=The Guardian|date=15 September 2021|access-date=15 September 2021}}</ref>

On 29 October, two days before the [[2021 United Nations Climate Change Conference]], Insulate Britain protests blocked traffic from junctions 21 to 22 in Hertfordshire and 28 to 29 in Essex. 19 arrests were made.<ref>{{cite news|url=https://www.theguardian.com/environment/2021/oct/29/insulate-britain-protesters-arrested-walking-on-to-m25|title=Insulate Britain protesters arrested walking on to M25|date=29 October 2021|accessdate=6 December 2021}}</ref>

==Cultural references==
{{quotebox|quote=The M25 is a form of social control to ensure disruptive elements in society are neutralised by keeping a significant proportion of them in continual motion.|source=[[Will Self]]{{sfn|Hamilton|2015|p=6}}|align=right|width=18em}}

The M25 and the Dartford Crossing are known for frequent traffic jams. This was noticed before the entire road had been completed; at the official opening ceremony Margaret Thatcher complained about "those who carp and criticise". The jams have inspired derogatory names, such as "Britain's Biggest Car Park"<ref>{{cite news|url=https://www.itv.com/news/2016-10-29/m25-britains-biggest-car-park-turns-30/|title=M25 turns 30 : Ten facts about "Britain's Biggest Car Park"|work=ITV|date=29 October 2016|access-date=24 July 2019}}</ref> and songs (e.g., [[Chris Rea]]'s "[[The Road to Hell (song)|The Road to Hell]]").<ref>{{Cite news|url=http://arts.guardian.co.uk/fridayreview/story/0,,790672,00.html |title=Chris Rea interviewed by Will Hodgkinson, ''The Guardian'', Friday 13 September 2002 |access-date=31 January 2009 | location=London | date=13 September 2002}}</ref> Nevertheless, coach tours around the M25 have continued to run into the 21st century.<ref>{{cite news|url=https://www.theguardian.com/uk/2012/mar/12/m25-coach-tour-surprise-hit|title=M25 is UK's newest tourist attraction|newspaper=The Guardian|date=12 March 2012|access-date=21 May 2019}}</ref>

The M25 plays a role in the comedy-fantasy novel ''[[Good Omens]]'', as "evidence for the hidden hand of Satan in the affairs of Man".<ref name=independent_20161017/> The demon character, Crowley, had manipulated the design of the M25 to resemble a Satanic [[Sigil (magic)|sigil]], and tried to ensure it would anger as many people as possible to drive them off the path of good.<ref>{{cite book |last1=Pratchett|first1=Terry|last2=Gaiman|first2=Neil|title=Good Omens|year=1993|publisher=Corgi Books|location=London|isbn=0552137030|page=19}}</ref><ref name="Gaiman 2003">{{cite web|author=[[Neil Gaiman]]|url=http://journal.neilgaiman.com/2003/04/image-stolen-from-patrick-nielsen.asp?m=1|title=Neil Gaiman's Journal|work=[[HarperCollins]]|publisher=[[News Corp (2013–present)|News Corp]]|date=11 April 2003|access-date=25 March 2017}}</ref> The lengthy series of public inquiries for motorways throughout the 1970s, particularly the M25, influenced the opening of ''[[The Hitchhiker's Guide to the Galaxy]]'', where the Earth is destroyed to make way for a hyperspace bypass.{{sfn|Hamilton|2015|p=10}}

The M25 enjoyed a more positive reputation among [[rave]]rs in the late 1980s, when this new orbital motorway became a popular route to the parties that took place around the outskirts of London.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-hereford-worcester-39960232|title=Castlemorton Common: The rave that changed the law|work=BBC News|date=28 May 2017|access-date=21 May 2019}}</ref> Its use for these raves inspired the name of the electronic duo [[Orbital (band)|Orbital]].<ref name=independent_20161017/>

[[Iain Sinclair]]'s 2002 book and film ''London Orbital'' is based on a year-long journey around the M25 on foot.<ref>{{cite news|last=Lezard|first=Nicholas|title=Meandering round the M25|url=https://www.theguardian.com/books/2002/sep/21/featuresreviews.guardianreview6|newspaper=The Guardian|date=21 September 2002}}</ref>

[[File:Give Peas A Chance - geograph.org.uk - 1723109.jpg|thumb|The "Give Peas a chance" graffiti on the Chalfont Viaduct, before its removal in 2018]]
A piece of [[graffiti]] on the [[Chalfont Viaduct]], clearly visible from the M25 and reading "Give Peas a chance" (parodying [[John Lennon]]'s "[[Give Peace a Chance]]") became popular with the public, attracting its own [[Facebook group]].<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-45564552|title='Give peas a chance' M25 bridge graffiti removed|work=BBC News|date=18 September 2018|access-date=29 May 2019}}</ref><ref>{{cite news|url=https://www.croydonadvertiser.co.uk/news/croydon-news/give-peas-chance-graffiti-m25-425872|title=Give pease a chance graffiti on M25|work=Croydon Advertiser|date=22 July 2016|access-date=29 May 2019}}</ref> The message originally read "Peas", supposedly the tag of a London graffiti artist; the rest of the wording is reported to have referred to his frequent clashes with the law.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-england-40485543|title=The landmarks that mean you're nearly home|work=BBC News|date=20 August 2017|access-date=29 May 2019}}</ref><ref>{{cite news|url=https://www.bbc.co.uk/news/magazine-13524208|title=Graffiti campaigns that stuck in the mind|work=BBC News Magazine|date=25 May 2011|access-date=29 May 2019}}</ref> In September 2018, after almost 20 years, the graffiti was vandalised and then removed and replaced with the message "Give Helch a break".<ref name=bbc_20180921>{{cite news|url=https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-45593174|title=Petition calls for M25 'give peas a chance' graffiti return|date=21 September 2018|access-date=19 July 2019}}</ref> A spokesman for [[Network Rail]] sympathised with the requests to restore the "much-loved graffiti", but said they do not condone people putting their lives at risk by trespassing.<ref name=bbc_20180921/><ref>{{cite news|url=https://www.standard.co.uk/news/uk/motorists-devastated-as-iconic-give-peas-a-chance-m25-graffiti-is-erased-a3941311.html|title=Motorists devastated as iconic "Give Peas A Chance" M25 graffiti is erased|work=London Evening Standard|date=20 September 2018|access-date=29 May 2019}}</ref>

==Junctions and services==
Data from [[driver location signs]] provide carriageway identifier information.<ref name=DLS>{{cite web|url=http://www.highways.gov.uk/business/documents/070921-Final_DLS_map.pdf |title=M25 Road Network Driver Location Signs |publisher=[[Highways Agency]]  |access-date=9 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110605140242/http://www.highways.gov.uk/business/documents/070921-Final_DLS_map.pdf |archive-date=5 June 2011 }}</ref> The numbers on the signs are kilometres from a point on the north side of the Dartford Crossing, while the letter is "A" for the clockwise carriageway and "B" for the anticlockwise. They are spaced every {{convert|500|metres}}.{{sfn|Hamilton|2015|p=26}}

The M25 has been criticised for having too many junctions; 14 of them serve only local roads.{{sfn|Asher|2018|p=117}}<ref>{{cite book|title=Orbital Motorways: Proceedings of the Conference Organized by the Institution of Civil Engineers and Held in Stratford-upon-Avon on 24–26 April 1990|page=131|publisher=Thomas Telford|year=1990|isbn=978-0-727-71591-3}}</ref> In 2016, [[Edmund King (campaigner)|Edmund King]], president of the [[The Automobile Association|Automobile Association]], attributed congestion on the M25 to excessive junctions. This leads to "junction hoppers" who only use the motorway for a short distance before exiting;{{sfn|Moran|2005|p=99}} their difference in speed when entering and leaving the main carriageway causes a [[domino effect]], resulting in all vehicles slowing down.<ref>{{cite news|url=https://www.standard.co.uk/news/transport/plan-for-smart-junctions-to-end-gridlock-on-m25-a3222156.html|title=Plan for "smart" junctions to end gridlock on the M25|work=London Evening Standard|date=11 April 2016|access-date=28 May 2019}}</ref> Drivers who only use the M25 to travel a short distance are believed by some to have less overall driving experience, exacerbating traffic and safety issues.{{sfn|Moran|2005|p=99}}

The M25 originally opened without any service areas. The first, at [[South Mimms services|South Mimms]], was opened by Margaret Thatcher in June 1987, a week before the election. Thatcher admired the practical and no-frills architecture of [[Charles Forte]] and praised him in her opening speech.{{sfn|Moran|2009|p=156}} The second, [[Clacket Lane services|Clacket Lane]], was opened by [[Robert Key (politician)|Robert Key]], Minister for Roads and Traffic, on 21 July 1993.{{sfn|Baldwin|Bridle|Baldwin|Porter|2002|p=938}} Construction was delayed as the remains of a [[Roman villa]] were found on the site, requiring archaeological research.{{sfn|Baldwin|Bridle|Baldwin|Porter|2002|p=764}} The other service area between junctions is [[Cobham services|Cobham]], which opened on 13 September 2012.<ref name=CobhamOpen/>

{| class="wikitable"
|- align="center" bgcolor="00703C" style="color: #FFD200;"
| colspan="6" | A282 (Dartford Crossing)
|-
!scope=col| miles
!scope=col| km<ref name=DLS />{{efn|The table gives details of each junction, including the roads interchanged and the destinations that are signed from the motorway on the blue advance direction signs. Figures in kilometres are from the driver location signs; figures in miles are derived from them.}}
!scope=col| Clockwise exits (A carriageway)<ref name=DLS />
!scope=col| Junction
!scope=col| Anti-clockwise exits (B carriageway)
!scope=col| Opening date{{sfn|Asher|2018|p=121}}
|- align="center"
|0.0
|0.0
|style="background:#dcdcfe;"| [[Dartford Crossing]] South<br />(Queen Elizabeth II Bridge)<br />[[File:UK traffic sign symbol NS67.svg|40px]]
! scope=row| [[River Thames|River<br />Thames]]
|style="background:#dcdcfe;"| Dartford Crossing North<br />(Dartford Tunnels)<br />[[File:UK traffic sign symbol NS67.svg|40px]]
| November 1963 (west tunnel)<br />May 1980 (east tunnel)<br />October 1991 (bridge)
|- style="text-align:center;"
|
|
|  ''Entering [[Kent]]''
|
|  ''Entering [[Essex]]''
| 
|- align="center"
|3.5
|5.7
| [[Swanscombe]], [[Erith]], [[Bluewater (shopping centre)|Bluewater]] [[A206 road|A206]]
! scope=row| J1A{{efn|Junctions 1A and 1B are part of the A282, though they use the M25's numbering scheme.<ref>{{cite web|url=https://www.roads.org.uk/motorway/m25|title=M25|website=roads.org.uk|access-date=19 July 2019}}</ref>}}
| Swanscombe, Erith A206
| September 1986
|- align="center"
|4.7
|7.5
| [[Dartford]] [[A225 road|A225]]
! scope=row| J1B
|{{no2}} '''No Exit'''
| September 1986
|- align="center" bgcolor="0080d0" style="color: white;"
| colspan="6" | M25
|-
|- align="center"
|5.5
|8.8
|  [[London]] (SE & C), [[Bexleyheath]] [[A2 road (Great Britain)|A2]]<br />[[Canterbury]] ([[M2 motorway (Great Britain)|'''M2''']])<br />''[[Ebbsfleet International]] [[File:British Rail - colour reversed logo.svg|x15px]]''<br /><br />''Non Motorway Traffic''
! scope=row| J2
|  London (SE & C), Bexleyheath, [[Bluewater (shopping centre)|Bluewater]] [[A2 road (Great Britain)|A2]]<br /> Canterbury ([[M2 motorway (Great Britain)|'''M2''']])<br />[[Dartford]] ([[A225 road|A225]])<br />''Ebbsfleet International [[File:British Rail - colour reversed logo.svg|x15px]]''
|September 1986 (northbound)<br />April 1977 (southbound)
|- align="center"
|8.7
|14.0
| [[Dover]], [[Channel Tunnel]], [[Maidstone]] [[M20 motorway|'''M20''']]<br />[[London]] (SE), [[Swanley]] [[A20 road (England)|A20]]
! scope=row| J3
| London (SE & C), [[Lewisham]] A20<br />Channel Tunnel, Maidstone '''M20'''
|April 1977 (northbound)<br />February 1986 (southbound)
|- align="center"
|12.2
|19.6
| [[Bromley]] [[A21 road (England)|A21]]<br />[[Orpington]] [[A224 road|A224]]
! scope=row| J4
| [[London]] (SE), Bromley A21<br />Orpington A224
| February 1986
|- align="center"
|16.3<br />16.4
|26.2<br />26.4
| [[Sevenoaks]], [[Hastings]] [[A21 road (England)|A21]]
! scope=row| J5
| [[Dover]], [[Channel Tunnel]], [[Maidstone]]<br />[[M26 motorway|'''M26''']] ([[M20 motorway|'''M20''']])<br />Sevenoaks, Hastings A21
| July 1980
|- style="text-align:center;"
|
|
|  ''Entering [[Surrey]]''
|
|  ''Entering [[Kent]]''
| 
|- align="center"
|21.0
|33.8
|[[Clacket Lane services]]
! scope=row| Services
|[[Clacket Lane services]]
|July 1993
|- align="center"
|25.8
|41.6
| [[Eastbourne]], [[Godstone]], [[Caterham]] [[A22 road|A22]]<br />[[Redhill, Surrey|Redhill]], [[Westerham]] ([[A25 road|A25]])
! scope=row| J6
| Eastbourne, Godstone, Caterham A22<br />Westerham (A25)
| November 1979 (eastbound)<br />February 1976 (westbound)
|- align="center"
|28.6
|46.0
| [[Brighton]], [[Crawley]]<br />[[Gatwick Airport|Gatwick]] {{rail-interchange|air}}<br />[[Croydon]]<br />[[M23 motorway|'''M23''']]
! scope=row| J7
| Croydon<br />Brighton, Gatwick {{rail-interchange|air}}<br />'''M23'''
| February 1976
|- align="center"
|31.9
|51.4
| [[Reigate]], [[Sutton, London|Sutton]] [[A217 road|A217]]<br />[[Kingston upon Thames|Kingston]] ([[A240 road|A240]])
! scope=row| J8
| Reigate, Sutton A217 <br />Redhill (A25)
| February 1976 (eastbound)<br />October 1985 (westbound)
|- align="center"
|38.5<br />39.5
|62.0<br />63.5
| [[Leatherhead]] [[A243 road|A243]]<br />[[Dorking]] ([[A24 road (Great Britain)|A24]])
! scope=row| J9
| Leatherhead A243<br />Dorking (A24)
| October 1985
|- align="center"
|42.6<br />43.2
|68.6<br />69.5
| [[Cobham services]]
! scope=row| Services
|[[Cobham services]]
|September 2012
|- align="center"
|45.0
|72.4
| [[Portsmouth]], [[Guildford]], [[London]] (SW & C)<br />[[A3 road|'''A3''']]
! scope=row| J10
| London (SW), Kingston, Guildford, Portsmouth<br />[[A3 road|'''A3''']]
| October 1985 (eastbound)<br />December 1983 (westbound)
|- align="center"
|49.8
|80.2
| [[Woking]] [[A320 road|A320]]<br />[[Chertsey]] [[A317 road|A317]]
! scope=row| J11
| Chertsey A317<br />Woking A320
| December 1983 (southbound)<br />October 1980 (northbound)
|- align="center"
|52.1
|83.8
| [[Basingstoke]], [[Southampton]]<br />[[Richmond, London|Richmond]]<br />[[M3 motorway (Great Britain)|'''M3''']]
! scope=row| J12
| The SOUTH WEST, Southampton<br />London (SW & C), Richmond<br />'''M3'''
| October 1980 (southbound)<br />December 1976 (northbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Berkshire]]''
|
|  ''Entering [[Surrey]]''
| 
|- style="text-align:center;"
|
|
|  ''Entering [[Surrey]]''
|
|  ''Entering [[Berkshire]]''
| 
|- align="center"
|55.2
|88.8
| [[London]] (W), [[Hounslow]], [[Staines-upon-Thames|Staines]] [[A30 road|A30]]
! scope=row| J13
| London (W), Hounslow, Staines A30
| November 1981 (southbound)<br />August 1982 (northbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Greater London]]''
|
|  ''Entering [[Surrey]]''
| 
|- align="center"
|57.0
|91.8
| [[Heathrow Airport|Heathrow]] {{rail-interchange|air}}<br />(Terminals 4, 5 & Cargo) [[A3113 road|A3113]]
! scope=row| J14
| Heathrow {{rail-interchange|air}} (Terminals 4, 5 & Cargo) [[A3113 road|A3113]]
| August 1982 (southbound)<br />September 1985 (northbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Buckinghamshire]]''
|
|  ''Entering [[Greater London]]''
| 
|- align="center"
|59.0
|95.0
| The WEST, [[Reading, Berkshire|Reading]], [[Slough]]<br />[[London]] (W & C), [[Heathrow Airport|Heathrow]] {{rail-interchange|air}} (Terminals 1, 2 & 3)<br />[[M4 motorway|'''M4''']] 
! scope=row| J15
| London (W), Heathrow {{rail-interchange|air}} (Terminals 1, 2 & 3)<br />The WEST, Slough, Reading<br />'''M4'''
| September 1985
|- align="center"
|63.8
|102.6
|  [[Birmingham]], [[Oxford]]<br />[[Uxbridge]], [[London]] (W)<br />[[M40 motorway|'''M40''']]
! scope=row| J16
|  Uxbridge, London (W & C)<br />Birmingham, Oxford<br />'''M40'''
| September 1985 (southbound)<br />January 1985 (northbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Hertfordshire]]''
|
|  ''Entering [[Buckinghamshire]]''
|
|- align="center"
|68.7
|110.5
| [[Rickmansworth]], [[Maple Cross]] A412
! scope=row| J17
| Maple Cross A412
| January 1985 (southbound)<br />February 1976 (northbound)
|- align="center"
|69.9
|112.5
| [[Amersham]], [[Chorleywood]] [[A404 road|A404]]
! scope=row| J18
| Amersham, Chorleywood, Rickmansworth A404
| February 1976
|- align="center"
|71.5
|116.4
| [[Watford]] [[A41 road|A41]]
! scope=row| J19
|{{no2}} Exit via J20 – Watford A41
| September 1976
|- align="center"
|73.5
|118.2
| [[Aylesbury]], [[Hemel Hempstead]] A41
! scope=row| J20
| Aylesbury, Hemel Hempstead, Watford A41
| August 1986
|- align="center"
|76.3
|122.8
| The NORTH<br />[[London Luton Airport|Luton]] {{rail-interchange|air}}<br />[[M1 motorway|'''M1''']]
! scope=row| J21
| The NORTH<br />Luton {{rail-interchange|air}}<br />'''M1'''
| August 1986
|- align="center"
|76.9
|123.7
| (M1 South)<br />[[St Albans]], [[London]] (NW & C) [[A405 road|A405]]
! scope=row| J21A
| (M1 South)<br />St Albans, London (NW & C), Watford A405
| August 1986
|- align="center"
|80.6
|129.7
| [[St Albans]] [[A1081 road|A1081]]
! scope=row| J22
| St Albans A1081
| August 1986
|- align="center"
|83.3
|134.0
| [[Hatfield, Hertfordshire|Hatfield]] [[A1(M) motorway|'''A1(M)''']]<br />[[London]] (N & C) [[A1 road (Great Britain)|A1]]<br />[[Chipping Barnet|Barnet]] [[A1081 road|A1081]]<br />''[[South Mimms services]]''
! scope=row| J23
| London (N & C) A1<br />Barnet A1081<br />Hatfield '''A1(M)'''<br />''South Mimms services''
| August 1986 (westbound)<br />September 1975 (eastbound)
|- align="center"
|85.9
|138.2
| [[Potters Bar]] [[A111 road (England)|A111]]
! scope=row| J24
| Potters Bar A111
| September 1975 (westbound)<br />June 1981 (eastbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Greater London]]''
|
|  ''Entering [[Hertfordshire]]''
| 
|- align="center"
|91.4
|147.1
| [[London]] (N & C)<br />[[Enfield Town|Enfield]], [[Hertford]] [[A10 road (England)|A10]]
! scope=row| J25
| London (N & C)<br />Enfield, Hertford A10
| June 1981 (westbound)<br />January 1984 (eastbound)

|- align="center"
|
|
| ''Holmesdale Tunnel''
! scope=row| ''Tunnel''
| ''Holmesdale Tunnel''
| January 1984
|- align="center"

|- style="text-align:center;"
|
|
|  ''Entering [[Essex]]''
|
|  ''Entering [[Greater London]]''
| 
|- align="center"
|94.9
|152.7
| [[Waltham Abbey (town)|Waltham Abbey]], [[Loughton]] [[A121 road (England)|A121]]
! scope=row| J26
| Waltham Abbey, Loughton A121
| January 1984
|- align="center"
|
|
| ''Bell Common Tunnel''
! scope=row| ''Tunnel''
| ''Bell Common Tunnel''
| January 1984
|- align="center"


|99.2
|159.7
| [[Cambridge]], [[Stansted Airport|Stansted]] {{rail-interchange|air}}, [[Harlow]]<br />[[London]] (N & E)<br />[[M11 motorway|'''M11''']]
! scope=row| J27
| London (NE & C)<br />Cambridge, Harlow, Stansted {{rail-interchange|air}}<br />'''M11'''
| January 1984 (westbound)<br />April 1983 (eastbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Greater London]]''
|
|  ''Entering [[Essex]]''
| 
|- align="center"
|107.1
|172.4
| [[Chelmsford]], [[London]] (E & C), [[Romford]] [[A12 road (England)|A12]] <br />[[Brentwood, Essex|Brentwood]] [[A1023 road|A1023]] 
! scope=row| J28
| Chelmsford A12<br />Brentwood A1023
| April 1983
|- style="text-align:center;"
|
|
|  ''Entering [[Essex]]''
|
|  ''Entering [[Greater London]]''
| 
|- style="text-align:center;"
|
|
|  ''Entering [[Greater London]]''
|
|  ''Entering [[Essex]]''
| <small>{{coord|54.17005|N|2.73748|W|dim:4000_region:GB|display=inline}}</small>
|- align="center"
|109.9
|176.8
| [[Southend]], [[Southend Airport]] {{rail-interchange|air}}, [[Basildon]] [[A127 road|A127]]
! scope=row| J29
| [[London]] (E & C), Romford, Southend, Southend Airport {{rail-interchange|air}}, Basildon A127
| April 1983 (northbound)<br />December 1982 (southbound)
|- style="text-align:center;"
|
|
|  ''Entering [[Essex]]''
|
|  ''Entering [[Greater London]]''
| 
|- align="center"
|115.2
|185.4
| [[Tilbury]], [[Thurrock]], [[Lakeside Shopping Centre|Lakeside]], [[London]] (E & C) [[A13 road (Great Britain)|A13]]<br />''[[Thurrock services]]''
! scope=row| J30
| [[London]] (E & C), Tilbury, Thurrock, Lakeside [[A13 road (Great Britain)|A13]]<br />''Thurrock services''<br /><br />''Non Motorway Traffic''
| December 1982
|- align="center"
|- align="center" bgcolor="00703C" style="color: #FFD200;font-size:120%;"
| colspan="6" | A282 (Dartford Crossing)
|- align="center"
|115.9
|186.6
|{{no2}} '''No Exit'''
! scope=row| J31
| [[Thurrock]], [[Lakeside Shopping Centre|Lakeside]] [[A roads in Zone 1 of the Great Britain numbering scheme|A1306]]<br />[[Purfleet]] ([[A1090 road|A1090]])<br />[[West Thurrock]] ([[A126 road|A126]])<br />''Thurrock services''
| December 1982
|- align="center"
|
|
|style="background:#dcdcfe;"| [[Dartford Crossing]] South<br />(Queen Elizabeth II Bridge)<br />[[File:UK traffic sign symbol NS67.svg|40px]]
! scope=row| [[River Thames|River<br />Thames]]
|style="background:#dcdcfe;"| Dartford Crossing North<br />(Dartford Tunnels)<br />[[File:UK traffic sign symbol NS67.svg|40px]]
| November 1963 (west tunnel)<br />May 1980 (east tunnel)<br />October 1991 (bridge)
|- style="text-align:center;"
|
|
|  ''Entering [[Kent]]''
|
|  ''Entering [[Essex]]''
| 
|-
|colspan=6|'''Notes'''
*Distances in kilometres and carriageway identifiers are obtained from [[driver location signs]]/location marker posts. Where a junction spans several hundred metres and the data is available, both the start and finish values for the junction are shown.
|-
{{jctbtm|keys=incomplete,toll}}

==References==
=== Explanatory notes ===
{{Notelist|refs=
{{efn|name=Berliner_Ring_is_longer|text=Since the completion of the M25, the [[Bundesautobahn 10|Berliner Ring]] has been completed to run at a slightly longer {{convert|196|km|abbr=on}}{{sfn|Hamilton|2015|p=20}}}}
}}

=== Citations ===
{{Reflist|30em}}

=== General and cited sources ===
{{Refbegin}}
* {{cite book|first=Wayne|last=Asher|title=Rings Around London: Orbital motorways and the battle for homes before roads|publisher=Capital History|year=2018|isbn=978-1854144218}}
* {{cite book|last1=Baldwin|first1=Peter|last2=Bridle|first2=Ron|last3=Baldwin|first3=Robert|last4=Porter|first4=John|title=The Motorway Achievement, Volume 1|publisher=Thomas Telford|year=2002|isbn=978-0-727-73196-8}}
* {{cite book|last=Bramley|first=J. F.|title=Roads for Britain: a digest of plans of future highways|edition=2nd|publisher=Staples Press|year=1946}}
* {{cite book|last=Hamilton|first=Ray|title=M25: A Circular Tour of the London Orbital|publisher=Summersdale Publishers|year=2015|isbn=978-1-783-72656-1}}
* {{cite book|last=Moran|first=Joe|title=Reading the Everyday|publisher=Routledge|year=2005|isbn=978-0-415-31709-2}}
* {{cite book|last=Moran|first=Joe|title=On Roads: A Hidden History|publisher=Profile Books|year=2009|isbn=978-1-846-68052-6}}
* {{cite book|last=Smith|first=Denis|title=London and the Thames Valley|publisher=Thomas Telford|year=2001|isbn=978-0-727-72876-0}}
* {{cite web|author=United Nations Economic Commission for Europe |date=1 November 2016 |title=ECE/TRANS/SC.1/2016/3/Rev.1: European Agreement on Main International Traffic Arteries |url=https://www.unece.org/fileadmin/DAM/trans/doc/2016/sc1/ECE-TRANS-SC1-2016-03-Rev1e.pdf}}
{{Refend}}

==Further reading==
* {{Citation |author-link=Iain Sinclair |first=Iain |last=Sinclair |title=London Orbital: A Walk Around the M25 |year=2002 |location=London |publisher=Granta Books |isbn=1-86207-547-6|ref=none }}.
* {{Citation |author-link=Roy Phippen |first=Roy |last=Phippen |title=Travelling M25 Clockwise |year=2005 |location=London |publisher=Pallas Athene |isbn=1-873429-90-8|ref=none }}.

==External links==
{{Commons category}}
{{Attached KML|display=inline,title}}
* [[Highways Agency]] – [https://highwaysengland.co.uk/roadworks-search/?days=0&region=all-regions&county=all-counties&location=&radius=10&roadlist=&severity=Severe Roadworks] {{Webarchive|url=https://web.archive.org/web/20200808140625/https://highwaysengland.co.uk/roadworks-search/?days=0&region=all-regions&county=all-counties&location=&radius=10&roadlist=&severity=Severe |date=8 August 2020 }}
* [[Highways Agency]] – [https://web.archive.org/web/20120914115834/http://www.highways.gov.uk/traffic/traffic.aspx Current Traffic Information]
* [[Highways Agency]] – [https://web.archive.org/web/20080802114933/http://www.dartfordrivercrossing.co.uk/drc/aboutf.htm Dartford – Thurrock River Crossing]
* [https://web.archive.org/web/20090720023542/http://www.iht.org/motorway/londonm25.htm The Motorway Archive's M25 page]
* [http://www.cbrd.co.uk/motorway/m25/ CBRD M25 Motorway Database]
* [https://web.archive.org/web/20061201054436/http://www.cbrd.co.uk/histories/openingbooklets/ CBRD M25 Opening Booklet]
* [https://londonist.com/london/best-of-london/wonders-of-the-m25 Wonders of the M25] – Londonist

{{UK motorways}}
{{Motorways and Trunk Roads in England}}
{{Transport in Buckinghamshire}}
{{Roads in London}}
{{Authority control}}

{{DEFAULTSORT:2-0025}}
[[Category:M25 motorway| ]]
[[Category:Constituent roads of European route E30]]
[[Category:Motorways in England]]
[[Category:Motorways in London]]
[[Category:Ring roads in London|M25]]
[[Category:Roads in Berkshire]]
[[Category:Roads in Essex]]
[[Category:Roads in Hertfordshire]]
[[Category:Roads in Kent]]
[[Category:Roads in Surrey]]
[[Category:Streets in the London Borough of Enfield]]
[[Category:Transport in Buckinghamshire]]
[[Category:Transport in Epping Forest District]]
[[Category:Transport in the London Borough of Enfield]]
[[Category:Transport in Thurrock]]