M25 motorway

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Traffic on the M25 near Heathrow Airport
The M25 (in blue)

The M25 motorway, or London Orbital motorway is a motorway 117 miles long that forms a vast ring around the metropolitan conurbation about London, passing through six counties: Middlesex, Essex, Kent, Surrey, Buckinghamshire and Hertfordshire. In Europe only one orbital road exceeds it in length; the Berliner Ring of 122 miles.

The M25 is one of the busiest and most congested parts of the British motorway network: 196,000 vehicles were recorded in a single day near Heathrow Airport. Plans to widen additional sections to eight lanes (four each way) were scaled back in 2009 in response to rising costs.[1]

A London orbital motorway was first suggested early in the 20th century as part of the plan to build four ring roads around London. A few sections, based on the now abandoned London Ringways plan, were constructed in the early 1970s and it was completed in 1986.


Map of the M25 showing width and schemes

The M25 was originally built mainly as a dual three-lane motorway, but much of the motorway has subsequently been widened to dual four-lanes in places and to a dual five-lane section between junctions 12 and 14 in Surrey and Middlesex, and a dual six-lane between junctions 14 and 15 in Middlesex and Buckinghamshire. Further widening is in progress with plans for "managed motorways" on other sections.

The M25 is not a strictly continuous loop because between Kent and Essex its route crosses the River Thames between Thurrock and Dartford as the A282 road. This section, the Dartford Crossing, consists of two tunnels and the Queen Elizabeth II Bridge. Passage across the bridge or through the tunnels is subject to a toll. Were this stretch of road made a motorway, this would prevent any traffic not permitted to use motorways from crossing the Thames east of the Woolwich Ferry.

The distance of the motorway from Charing Cross, the traditional waypoint for central London, varies from about 12 miles near Potters Bar to 20 miles near Byfleet.

"Within the M25" is often used as a shorthand for the London conurbation, but some major towns which are free of the latter yet find themselves within the ring of the M25, such as such as Epsom (Surrey), Watford (Hertfordshire) and Loughton (Essex).


The M25 has four service areas:

  • South Mimms services (Junction 23, Middlesex)
  • Clacket Lane services (Surrey, between Junctions 5 and 6) and
  • Thurrock services (Junction 30, Essex).
  • A fourth service area opened near Cobham, Surrey in 2012.


Plans and construction

The M25 motorway between junctions 14 and 15, near Heathrow Airport
The M4/M25 motorway junction, near Heathrow Airport
The M25 between junction 24 (Potters Bar) and 25 (Waltham Cross)
The M25 between junctions 7 (M23) and 6, near Reigate

The idea of an orbital road around London was first proposed early in the 20th century and then re-examined in Sir Charles Bressey's and Sir Edwin Lutyens' The Highway Development Survey, 1937. Sir Patrick Abercrombie's County of London Plan, 1943 and Greater London Plan, 1944 proposed a series of five roads encircling the capital. The northern sections of the M25 follow a similar route to the Second World War Outer London Defence Ring.

Little was done to progress these plans until the 1960s when the Greater London Council developed their London Ringways plan which consisted of four 'rings' around the capital. Sections of the two outer rings - Ringway 3 (the 'M16 motorway') and Ringway 4 were constructed in the early 1970s and these were later integrated into the single M25 orbital motorway. The Ringways plan was however hugely controversial due to the destruction required for the inner two ring roads (Ringway 1 and Ringway 2). Parts of Ringway 1 were constructed (including West Cross Route and Westway) against stiff opposition before the overall plan was abandoned in 1973 following pressure from residents in the threatened areas.

Construction of parts of the two outer ring roads, Ringways 3 and 4, were however started in 1973. The first section, between South Mimms and Potters Bar in Middlesex (junction 23 to junction 24) opened in September 1975 and was given the temporary general purpose road designation A1178; a section south of London (junction 6 to junction 8) opened in 1976. A section of Ringway 3 south of the river between Dartford and Swanley (junction 1 to junction 3) was constructed between 1974 and 1977.

In 1975 the plans for Ringway 3 were modified to combine it with Ringway 4, the outermost Ringway. The combined motorway was given the designation M25 which had originally been intended for the southern and western part of Ringway 4 and the M16 designation was dropped. The section of Ringway 3 west of South Mimms anti-clockwise around London to Swanley in Kent was cancelled. The stages were not constructed contiguously but in small sections. 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 section from Potters Bar to the Dartford Tunnel was constructed between 1979 and 1982. Construction of the M25 continued in stages until its completion in 1986. Prime Minister Margaret Thatcher officially opened the M25 on 29 October 1986, with a ceremony in the section between J22 and J23 (London Colney and South Mimms). The initial tenders for the construction of the M25 totalled £631.9 million, excluding the cost of compulsory purchase of land and subsequent upgrades and repairs.

Operational history

Soon after the motorway opened in 1986 traffic levels exceeded maximum designed capacity and in 1990 the Secretary of State for Transport announced plans to widen the whole of the M25 to four lanes.[2] By 1993 the motorway that was designed for a maximum of 88,000 vehicles a day was carrying 200,000,[3] 15% of UK motorway traffic volume was on the M25 and there were plans to add 6 lanes to the section from Junction 12 to 15 as well widening the rest of the motorway to 4 lanes[4]

In 1995 a contract was awarded to widen the section between junctions 8 and 10 from six to eight lanes for a cost of £93.4 million[5] and a Motorway Incident Detection and Automatic Signalling (MIDAS) system was introduced to the M25 from junction 10 to junction 15 at a cost of £13.5m in 1995 and then extended to junction 16 at a cost of £11.7m in 2002. This consists of a distributed network of traffic and weather sensors, speed cameras and variable-speed limit signs that control traffic speeds with little human supervision, and has improved traffic flow slightly, and reduced the amount of start-stop driving.[6]

In 1995 there was a proposal to widen the section close to Heathrow Airport to 14 lanes. This attracted fierce opposition from road protesters opposing the Newbury Bypass and other schemes[7] and it was cancelled shortly afterwards.[8] However, in 1997 the Department of Transport announced new proposals to widen the section from junction 12 (M3) and junction 15 (M4) to 12 lanes. At the Heathrow Airport Terminal Five public inquiry a Highways Agency official said that the widening was needed to accommodate traffic to the proposed new terminal, however the transport minister said that no such evidence had been given.[9] Environmental groups objected to the decision to go ahead a scheme that would create the widest motorways in the UK without holding a public inquiry.[10] The decision was again deferred. A decision to go-ahead was given for a 10-lane scheme in 1998[11] and the £148 million 'M25 Jct 12 to 15 Widening' contract was awarded to Balfour Beatty in 2003.[12] The scheme was completed in 2005 as dual-five lane between junctions 12 to 14 and dual six lanes from 14 to 15.[13]

In 2007 capacity at junction 25 (A10/Waltham Cross) was increased and the Holmesdale Tunnel was widened to 3 lanes in an eastern direction at a cost of £75 million.[14]

Work to widen the exit slip-roads in both directions at Junction 28 (A12 road/A1023) was completed in 2008. It was designed 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.[15]

Design, Build, Finance and Operate (DBFO) contract

In 2006 the Highways Agency proposed to widen 63 miles of the M25 from six to eight lanes, between junctions 5-6 and 16-30 as part of a Design, Build, Finance and Operate (DBFO) project, and in June 2009 the new transport minister indicated that the cost had risen to £5.5 billion and the benefit to cost ratio had dropped considerably.[16] In January 2009 the government announced that plans to widen the sections from Junction 5-7 and from 23-27 had been 'scrapped' and that hard shoulder running would be introduced instead.[17]

In 2009 a £6.2 billion M25 'Design, Build, Finance and Operate' (DBFO) private finance initiative contract[18] was awarded to Connect Plus to widen the sections between junctions 16 and 23 and between junctions 27 and 30 and maintain the M25 and the Dartford Crossing for a 30-year period.[19]

Works to widen the section between junctions 16 and 23 (M40-A1(M)) to dual 4 lanes[20] started in July 2009 at an estimated cost of £580m;[21] The J16-21 section (M40 to M1) was completed by July 2011 and from J21-23 (M1 to the A1(M)) by June 2012.[22] Works to widen the J27-30 section (M11-A13) to dual 4 lanes started in July 2009. J27-28 (M11-A12) was completed in July 2010,[23] J28-29 (A12-A127) in June 2011 and J29-30 (A127-A13) in May 2012.[24]

Junctions 7-10: controlled motorway

A proposal to convert the section from Junctions 7 to 10 to 'controlled motorway' was put out to consultation between November 2009 and March 2010.[25] Work on installing the gantries were complete by April 2011[26] at which time the system was used to display advisory speeds. As of June 2012 it was stated that the legal process to make these speeds mandatory was likely to be complete by spring 2012.[27]


Other cities encircled by motorways include Manchester using the M60 motorway, Birmingham using parts of the M5, M6 and M42 and from 2011 Glasgow has had an orbital motorway made of the M8, M73 and M74, although one section of the route passes through the midst of the city.[28] The M25 is exceeded by just one ring road in Europe, namely the Berlin Ring (Bundesautobahn 10) which is 5 miles longer.

The M25 is one of the busiest motorways in Britain and Europe:

  • M25 around London: 196,000 vehicles a day recorded in 2003 between junctions 13 and 14 near Heathrow Airport.
  • Autobahn Südosttangente Wien (A23) (near Vienna): More than 200,000 vehicles on an average day.
  • Bundesautobahn 100 (A 100) (Berlin): 216,000 vehicles in a day were recorded in 1998
  • A4 autoroute (Paris): 257,000 vehicles a day recorded in 2002.[29]

Popular culture

The multi-level stack interchange junction with the M23

Iain Sinclair's book and film, London Orbital which was published in 2003 is based on a year long journey around the M25 on foot.[30]

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") and songs (Chris Rea's "The Road to Hell").[31]

The M25 plays an important role in the comedy-fantasy novel Good Omens, being "evidence for the hidden hand of Satan in the affairs of Man".[32]

The road enjoyed a more positive reputation among ravers in the late 1980s as the then new Orbital Motorway was a popular route to the parties that took place around the outskirts of London. The use of the M25 for these raves inspired the name of electronic duo Orbital.[33]


Data[34] from driver location signs provide carriageway identifier information, giving the distance from a point near the River Thames, east of London, when travelling clockwise on the motorway.

A282 road - Dartford Crossing
Junction miles Clockwise exits (A Carriageway)[34] Anti-clockwise exits (B Carriageway)
J1a 3.5 Erith A206 Erith A206, Swanscombe (A226)
J1b 4.7 Dartford A225 Exit via J2 - Dartford (A225)
M25 motorway - London Orbital
J2 5.5 London (South East), Canterbury A2, (M2), Bluewater London (SE & C), Lewisham A2(W), Canterbury A2(E) (M2), Dartford (A225)
J3 8.7 London (South East) A20
Maidstone M20
Swanley B2173
Maidstone, Channel Tunnel M20
London (SE & C), Lewisham A20
J4 12.2 Bromley A21
Orpington A224
Bromley, London (SE) A21
Orpington (A224)
J5 16.3–16.4 Sevenoaks, Royal Tunbridge Wells, Hastings A21 Maidstone, Channel Tunnel, Dover M26 (M20)
Sevenoaks, Hastings A21
Services 21.0 Clacket Lane services Clacket Lane services
J6 25.8 East Grinstead, Eastbourne, Caterham, Godstone A22
Westerham (A25)
Eastbourne, Caterham, Godstone A22, Westerham (A25)
J7 28.6 Gatwick Airport, Crawley, Brighton, East Grinstead, Croydon M23 Gatwick, Brighton, M23(S), Croydon M23(N)
J8 31.9 Reigate, Sutton A217
Redhill (A25)
Reigate, Sutton A217
Redhill (A25)
J9 38.5 -
Leatherhead A243
Dorking (A24)
Leatherhead A243
Dorking (A24)
Services 42.6 -
Cobham Services Cobham Services
J10 45.0 London (South West), Sutton, Guildford, Portsmouth A3 London (South West), Guildford, Portsmouth, A3
J11 49.8 Chertsey A317
Woking A320
Woking A320
Chertsey A317
J12 52.1 Basingstoke, Southampton, Richmond M3 Basingstoke, Southampton, Richmond M3
J13 55.2 A30 London (West), Hounslow, Staines A30 London (West), Hounslow, Staines
J14 57.0 Heathrow Airport (Terminals 4, 5 and Cargo) A3113 dedicated spur Heathrow Airport (Terminals 4, 5 and Cargo) A3113 dedicated spur
J15 59.0 The West, Slough, Reading, London (West), Heathrow Airport (Terminals 1, 2 and 3) M4 The West, Slough, Reading M4(W)
London (W), Heathrow (Terminals 1, 2 & 3) M4(E)
J16 63.8 The North Birmingham, Oxford, Uxbridge, London (W,C) M40 Birmingham, Oxford M40(W)
Uxbridge, London (W & C) M40(E)
J17 68.7 Maple Cross (A412) Maple Cross A412
J18 69.9 Rickmansworth, Chorleywood, Amersham A404 Chorleywood, Amersham, Rickmansworth A404
J19 71.5 Watford A41 No exit
J20 73.8 Hemel Hempstead, Aylesbury A41 Hemel Hempstead, Aylesbury, Watford A41
J21 76.3 The North, Luton & Airport M1 The North, Luton & Airport M1
J21A 76.9 Watford A405
Harrow (M1 South)
St Albans A405
London (North West) (M1 (South))
J22 80.6 London Colney A1081 St Albans A1081
83.3 Hatfield A1(M)
London (North West) A1
Barnet A1081
South Mimms services
Hatfield A1(M), London (NW) A1
Barnet A1081, Services
J24 85.9 Potters Bar A111 Potters Bar A111
J25 91.4 Enfield, Hertford A10 Enfield, Hertford, London (N & C) A10
J26 94.9 Waltham Abbey, Loughton A121 Waltham Abbey, Loughton A121
J27 99.2 London (NE), Stansted Airport, Harlow, Cambridge M11 London (NE & C) M11(N), Stansted, Harlow, Cambridge M11(S)
J28 107.1 Chelmsford, Witham, Colchester A12
Brentwood A1023
Chelmsford, Romford A12
Brentwood A1023
J29 109.9 Romford, Basildon, Southend A127 Basildon, Southend, Romford A127
J30 115.2 Dagenham, Rainham, Tilbury, Barking, London (E & C) A13
Thurrock services
Dagenham, Rainham, Tilbury, Basildon, London (E & C) A13, West Thurrock (A126)
A282 Road - Dartford Crossing
115.9 Access via J30 Thurrock (Lakeside), Services A1306, Purfleet (A1090), West Thurrock (A126)
River Dartford Crossing A282
Dartford Tunnel
Dartford Crossing A282
Queen Elizabeth Bridge


  1. Webster, Ben (2009-06-25). "Rising costs put the brakes on dozens of roadbuilding projects". The Times (London). http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6571879.ece. Retrieved 2010-05-12. 
  2. "HANSARD 3 December 1990 Written Answers (Commons) TRANSPORT". http://hansard.millbanksystems.com/written_answers/1990/dec/03/m25. 
  3. "The bluffer's briefing on: The M25". The Independent (London). 1993-03-24. http://www.independent.co.uk/news/uk/the-bluffers-briefing-on-the-m25-1499570.html. Retrieved 2010-05-12. 
  4. "M25 (Widening)". Hansard. http://hansard.millbanksystems.com/commons/1993/feb/18/m25-widening. 
  5. "M25 scoop for Balfour in Surrey". http://www.cnplus.co.uk/news/m25-scoop-for-balfour-in-surrey/955396.article. 
  6. "Case Study - M25 Controlled Motorway". Highways Agency. http://www.dft.gov.uk/itstoolkit/CaseStudies/m25-controlled-motorway.htm. 
  7. Wolmar, Christian (1995-04-04). "The roadblock that became a bandwagon". The Independent (London). http://www.independent.co.uk/news/uk/the-roadblock-that-became-a-bandwagon-1614137.html. Retrieved 2010-05-12. 
  8. Cohen, Nick (1995-04-02). "Pointless lies that reveal so much". The Independent (London). http://www.independent.co.uk/opinion/pointless-lies-that-reveal-so-much-1613955.html. Retrieved 2010-05-12. 
  9. Wolmar, Christian (1997-03-21). "Minister gives green light to widen M25". The Independent (London). http://www.independent.co.uk/news/minister-gives-green-light-to-widen-m25-1274054.html. Retrieved 2010-05-12. 
  10. "Plans to widen M25 to 12 lanes under attack". http://www.getsurrey.co.uk/news/s/80175_plans_to_widen_m25_to_12_lanes_under_attack. 
  11. "BAA makes plans for Terminal 5 despite inquiry". http://www.nce.co.uk/baa-makes-plans-for-terminal-5-despite-inquiry/845174.article. 
  12. "M25 Junctions 12 - 15 Widening". http://www.bbcel.co.uk/capabilities/roads/62_m25-junctions-12-15-widening. "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)." 
  13. "M25 Jct 12 to 15 Widening". Highways Agency. http://www.highways.gov.uk/roads/projects/4084.aspx. 
  14. "£75 "Million Refurbishment for M25 Holmesdale Tunnel and Junction 25 Improvement Work Starts on Saturday 6 May"". Highways Agency. http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=132377. 
  15. "M25 Junction 28 / A12 / Brook Street Interchange". Highways Agency. http://www.highways.gov.uk/roads/projects/3520.aspx. 
  16. "Cost escalation hits M25 widening benefit to cost ratios". http://www.nce.co.uk/major-projects/m25-widening/cost-escalation-hits-m25-widening-benefit-to-cost-ratios/5203578.article. 
  17. Helm, Toby (2009-01-18). "Ministers scrap plan to widen motorways". The Guardian (London). http://www.guardian.co.uk/politics/2009/jan/18/motorways-geoff-hoon. Retrieved 2010-05-12. 
  18. Webster, Ben (2009-05-20). "PFI deal for M25 agreed despite price rise". The Times (London). http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article6322870.ece. Retrieved 2010-05-12. 
  19. "£6.2 billion M25 Design, Build, Finance and Operate (DBFO) contract awarded". Highways Agency. http://www.highways.gov.uk/news/pressrelease.aspx?pressreleaseid=174136. 
  20. "M25 Jct 16 to 23 Widening". http://www.highways.gov.uk/roads/projects/5747.aspx. 
  21. "M25 widening to four lanes begins". BBC News. 2009-07-08. http://news.bbc.co.uk/1/hi/england/8139940.stm. Retrieved 2010-05-12. 
  22. "Highways Agency Timetable". http://www.highways.gov.uk/roads/projects/13825.aspx. 
  23. "Weekly Summary of Roadworks in M25 Sphere - 30 September 2009". http://www.fleetdirectory.co.uk/fleet-news/index.php/2009/09/30/weekly-summary-of-roadworks-in-m25-sphere-30092009/. 
  24. "M25 Jct 27 to 30 Widening". http://www.highways.gov.uk/roads/projects/5739.aspx. 
  25. "M25 J7 - J10 Controlled Motorway - Public Consultation". Highways Agency. http://webarchive.nationalarchives.gov.uk/+/http://www.highways.gov.uk/roads/27477.htm. 
  26. "M25 J7 to J10 Controlled Motorway Project". http://www.forwardspread.co.uk/2011/m25-j7-to-j10-controlled-motorways-project/. 
  27. "M25 J7-J10 controlled motorway". Highways Agency. http://www.highways.gov.uk/roads/projects/23473.aspx. Retrieved 1 May 2011. 
  28. "Transport Scotland - M74 Completion Project". http://www.transportscotland.gov.uk/projects/m74-completion/the-project. Retrieved 2009-09-06. 
  29. "Compte Rendu Analytique Officiel de la Seance du 17 Decembre 2002" (in French). http://www.senat.fr/cra/s20021217/s20021217H4.html. 
  30. "London Orbital [Paperback"]. Amazon. http://www.amazon.co.uk/dp/0141014741. 
  31. "Chris Rea interviewed by Will Hodgkinson, The Guardian, Friday 13 September 2002". London. 2002-09-13. http://arts.guardian.co.uk/fridayreview/story/0,,790672,00.html. Retrieved 2009-01-31. 
  32. "Good Omens Annotations". http://www.lspace.org/books/apf/good-omens.html. 
  33. "Orbital information". http://www.loopz.co.uk/info.html. Retrieved 28 January 2011. 
  34. 34.0 34.1 "M25 Road Network Driver Location Signs". Highways Agency. http://test1.highways.gov.uk/business/documents/070921-Final_DLS_map.pdf. Retrieved 2009-06-09. 

Further reading

  • Iain Sinclair (2002), London Orbital: A Walk Around the M25, London: Granta Books, ISBN 1-86207-547-6 .
  • Roy Phippen (2005), Travelling M25 Clockwise, London: Pallas Athene, ISBN 1-873429-90-8 .
  • Terry Pratchett; Gaiman, Neil (2006), Good Omens, New York: William Morrow, pp. 13–14, ISBN 0-06-085396-4 .

Outside links

("Wikimedia Commons" has material
about M25 motorway)
Motorways in the United Kingdom

Great Britain: M1  • M2  • M3  • M4  • M5  • M6  • M6 Toll  • M8  • M9  • M10  • M11  • M18  • M20  • M23  • M25  • M26  • M27  • M32  • M40  • M42  • M45  • M48  • M49  • M50  • M53  • M54  • M55  • M56  • M57  • M58  • M60  • M61  • M62  • M63  • M65  • M66  • M67  • M69  • M73  • M74  • M77  • M80  • M85  • M90  • M180  • M181  • M271  • M275  • M602  • M606  • M621  • M876  • M898  • Sections of A road: A1(M)

Former motorways marked in italics

Northern Ireland: M1  • M2  • M3  • M5  • M12  • M22