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M25 motorway (London Orbital)
Greater London, UK
M25 motorway (London Orbital)
associated engineer
Eastern Road Construction Unit
South East Road Construction Unit
W.S. Atkins
Mott Hay & Anderson
Greater London Council
date  1973 - October 1986
UK era  Modern  |  category  Road  |  reference  TQ311531
ICE reference number  HEW 2332
photo  By EricITOworld (Own work work over wikipedia:Openstreetmap data) [CC BY-SA 3.0 via Wikimedia Commons
The M25 motorway around London is one of the world’s biggest ring roads, though not technically a full circle — the Dartford Crossing section is part of the A282. The well-used traffic artery has attracted nicknames such as 'the road to hell' or 'the road to nowhere' and is frequently derided by commuters as no more than a car park. At the time it was completed, it was Britain’s most expensive motorway.
Proposals for a road to circle London began to be aired in the early 20th century. In 1905, William Rees Jeffreys (1872-1954) told the Royal Commission on London Transport that, "It was a disgrace that no road existed which encircled the English capital".
The commission suggested a ring road with a 7.7km radius. In the 1920s, construction of this M25 precursor began on both sides of the River Thames. The North Circular Road (A406) was completed around 1930. Its counterpart, the South Circular, a linked series of urban streets and new roads, was finished in the late 1930s. Both are still in heavy use, though much altered since then.
On 16th May 1938, the first coherent proposal for a London orbital route appeared in the Highways Development Survey 1937, prepared by engineer Sir Charles Herbert Bressey (1874-1951) and architect Sir Edwin Landseer Lutyens (1869-1944). It detailed plans for radial routes from, and circular routes around, the city centre. However, implementation of the proposals was delayed by the start of World War II (1939-45).
In 1944, Sir Patrick Abercrombie's (1879-1957) Greater London Plan, suggested a series of five ring roads around the capital to keep traffic moving. The existing North and South Circulars formed the ‘C’ (middle) ring.
On 1st April 1965, the Greater London Council came into being, created under the terms of the London Government Act 1963. The council’s 1969 Greater London Development Plan incorporated the London Transportation Survey (formerly the London Traffic Study). It retained Abercrombie’s radial and orbital road structure, dropping the innermost ‘A’ ring and proposing four ringways — a city centre ‘motorway box’, upgraded North and South Circulars, a suburban ring and an outer parkway (not a complete circuit).
This plan was abandoned in 1973. However, by that time construction had begun on the Department of Transport’s new stretches of motorway, north and south of London. The M16 to link the M1 directly with the Dartford Tunnel (opened November 1963) and the M25 to relieve the A25 through Surrey and Kent before joining the M20 near Wrotham.
The idea of a London orbital was resurrected and a joint planning team of national and local government was set up to develop an overall regional strategy for the south east of England. In November 1975, Minister of Transport John William Gilbert (1927-2013) announced that the M16 and M25 would be extended to meet at Egham in the west and at Dartford in the east, forming a London orbital motorway to be called the M25. Its route follows parts of the defunct suburban and parkway rings suggested in 1969, themselves a reworking of Abercrombie’s ‘D’ and ‘E’ circular roads.
The scheme was not without controversy — 39 separate public inquiries were held, totalling more than 700 days of hearings. Construction and opening were carried out piecemeal in stages under 41 separate contracts, including advance works. The completed motorway is 188km long and has two tunnels, 32 interchanges (nine of them complex ones) and more than 250 custom-designed bridges.
The M25’s junctions are numbered clockwise from the Kent (south) end of the Dartford Crossing, 1 to 31, with 21A being a separate interchange. The whole project was implemented by two teams of government engineers, overseeing the consultants and contractors involved with each contract.
The southern half of the M25, from Dartford to Staines (J1 to J13), was the responsibility of the South Eastern Road Construction Unit. The northern half of the M25, from Staines to Thurrock (J13 to J31), was handled by the Eastern Road Construction Unit until 1981 and the Eastern Regional Office (Transport) thereafter.
The first piece of the contract jigsaw was the 4.3km section from the A1 South Mimms to the A111 Potters Bar, between J23 and J24, opened to traffic in September 1975. The final length was the 21km stretch between J19 and J23 to the north of London, completed October 1986. Both pieces were constructed by the same contractor,
In 1976, 20.8km of motorway were built — from Godstone to Reigate (J6 to J8), between Thorpe and Egham (J12 to J13) and from Maple Cross to Hunton Bridge (J17 to J19). The work included constructing the four-level M23 interchange (J7) at Merstham, carrying the M23 over a five span steel box girder bridge 23m above the M25.
In 1977, 5.3km of the M25 were constructed between Dartford and Swanley (J1 to J3), including the three-level Swanley interchange (J3) with the M20 and A20. The link road to the motorway at Chertsey (J11) was also completed.
Much work was underway during 1978. In 1979, 14.4km of motorway were finished between Sundridge Road and Godstone (J5 to J6). Also built was Lyne Rail Bridge (TQ022670) south of J12 near Chertsey, once voted the world’s ugliest bridge by civil engineers. The two-span prestressed concrete bridge crosses the M25 at a 60-degree skew and its cable stayed design (Europe’s first for a railway bridge) necessitated heavy parapet walls to minimise flexure of the deck.
The long awaited second Dartford Tunnel (A282) opened in May 1980, enabling each bore to accommodate traffic travelling in one direction: northbound through the west tunnel, southbound through the east tunnel.
During 1980, 5.3km of motorway were completed (J11 to J12), along with two interchanges (J5 and J12), the advance bridges contract and the widening of Runnymede Bridge (TQ019719). This brick and masonry bridge crosses the Thames, and was designed by Lutyens in the 1940s (completed 1961) for the A30 Staines Bypass. It has been widened on its east side to a design by engineer Ove Arup, using a series of slender open-spandrel concrete arches to carry the M25 south of J13.
The M25 changes direction from south to west at the two-level free flow Sevenoaks interchange (J5), where it is joined by the M26 and A21. The Chertsey interchange (J12) with the M3 has a two-level cyclic design, better fitting the topography by extending over a large area but reducing the overall height. Bridge decks of voided reinforced concrete minimised construction depths.
In 1981, 10km of the M25 were built — from Egham to Yeoveney (J13), and between the A111 Potters Bar and the A10 Waltham Cross (J24 to J25).
A further 9.4km were completed in 1982, the stretches from Yeoveney to the A3113 Heathrow Airport spur at Poyle (J13 to J14), from the A127 North Ockendon interchange to the A13 Mar Dyke (J29 to J30), to Thurrock (J31) where the M25 joins the A282 for the north approach to the Dartford Tunnel.
In 1983, two more sections were finished, totalling 30.9km. The M25 from Wisley to Chertsey (J10 to J11) is carried over the River Wey navigation canal and a main rail line on New Haw Viaduct (TQ055621), a 285m long structure designed by Gifford, with seven spans of in situ post-tensioned concrete and a railway span of precast concrete beams. The other section runs from the two-level M11 interchange (J27), with its seven bridges, at Theydon Garnon to the A127 North Ockendon interchange (J29).
The 12.7km of motorway between the A10 Waltham Cross and the M11 Theydon Garnon (J25 to J27) were completed in 1984. To minimise the environmental impact here, the M25 passes through two cut-and-cover tunnels — Holmesdale Tunnel (TL354000 to TL360000) at Waltham Cross east of J25, and Bell Common Tunnel (TL445010 to TL450010) between J26 and J27 at the northern edge of Epping Forest.
in July 1984, four motorway service areas were proposed, one in each compass quadrant, at Clacket Lane in Surrey, Iver in Buckinghamshire, South Mimms in Hertfordshire and Thurrock in Essex. South Mimms (J23) services opened in 1986, Thurrock (J30 to J31) in 1992 and Clacket Lane (J5 to J6) in 1993. Planning debate led to the Iver services being relocated to Cobham (J9 to J10) in Surrey, opened 2012.
In 1985, 32.1km were completed — from Reigate to Wisley (J8 to J10), including the Leatherhead interchange (J9), and from the A3113 Heathrow Airport spur at Poyle to Maple Cross (J14 to J17), encompassing interchanges with the M4 (J15) and M40 (J16). Constructing the M4 junction provided one of the M25’s foremost challenges, fitting a four-level interchange with 11 bridge structures into flat terrain while maintaining traffic flow on the busy M4. The M40 interchange is on two levels with links and loops.
In 1986, the final sections of the M25 were completed, totalling 36.9km, stitching together the loop to close the circuit. The last pieces were the southern approach to the Dartford Tunnel (J1A to J2), between Swanley and Dunton Green (J3 to J5) and from Micklefield Green to the A1 South Mimms (J19 to J23), including the linked interchanges with the M1 (J21) and A405 (J21A). The M1 interchange is four-level structure while the A405 junction has a conventional roundabout above the M25.
The engineers that worked on the project are listed at the top of this article, shown in order of the proportion of the total project completed, as is the list of main contractors below.
One of the more noticeable structures on the M25 is an elegantly simple concrete arch (TQ505604), carrying an access pathway over the deep cutting of the motorway between Chelsfield and Sevenoaks (J4 to J5). It serves as a gateway to Kent and Surrey for road users travelling south.
Environmental considerations governed the alignment of the whole orbital route. A combination of following topographical contours and employing extensive earthworks, landscaping and tree planting the motorway’s overall impact on its surroundings. In certain sensitive areas, carriageway formations were cut some 3-4m lower than planned at the outset to harmonise with the terrain.
The roadway itself was constructed with areas of both rigid and flexible concrete pavements. High levels of noise for road users and changing technical specifications for roadbuilding resulted in much of the concrete being replaced by flexible construction or resurfaced with asphalt.
On 29th October 1986, the M25 Orbital Motorway was opened officially by prime minister Margaret Thatcher (1925-2013). It was then Britain's most expensive motorway and cost £909m (at 1986 prices).
Fears that traffic demand forecasts had been overestimated were quashed almost at once. The M25 was designed to carry a maximum of 88,000 vehicles per day. When it opened in 1986, traffic on the busiest Heathrow Airport section peaked at 113,000 vehicles per day. By 1993, the figure had risen to 200,000 vehicles per day.
The Department of Transport commissioned Rendel, Palmer & Tritton to investigate current and future traffic demands, with options for reducing traffic build-up and congestion. The report was published in 1989, and suggestions apparently included controversial hard shoulder running.
In 1990, the first M25 widening scheme was undertaken between Chertsey and Egham (J11 to J13), upgrading the motorway to four lanes in each direction.
On 30th October 1991, the Queen Elizabeth II Bridge opened at Dartford to carry A282 southbound traffic over the Thames. All the road’s northbound traffic could then use both tunnels. The combination of tunnels and cable-stayed bridge (then the longest in Europe) was renamed the Dartford Crossing.
In 1997, similar works were carried out between Westerham and Wisley (J6 to J10). Subsequent widening programmes increased the motorway to dual five-lane carriageways between Thorpe and Yeoveney (J12 to J14) and dual six-lane from Yeoveney to near Heathrow Airport (J14 to J15).
In 2005, the M25 became England’s first motorway to trial variable mandatory speed limits to reduce congestion. The system was introduced between Chertsey and the M4 interchange (J11 to J15), and has been extended to other busy sections of the circuit.
Between May 2006 and September 2007, the Holmesdale Tunnel was refurbished and the Waltham Cross interchange (J25) was widened to dual three lanes.
In October 2008, the Connect Plus consortium of Balfour Beatty, Skanska, Atkins and Egis began work to widen the 230m long Berry Lane Viaduct (TQ039955), constructed in 1978, near Chorleywood. The seven span reinforced concrete viaduct was extended seamlessly by 4.75m on each side, clockwise carriageway first. It crosses a London Underground rail line, a road and a natural valley, rising 16.5m above the valley floor.
The viaduct work was included in a design, build, finance and operate (DBFO) initiative as part of a £6.2 billion concession to improve the M25 network. The contract was awarded to Connect Plus in May 2009.
The project upgraded the motorway to dual four lanes between Sevenoaks and Merstham (J5 to J7) in the south, and between the M40 interchange and South Mimms (J16 to J23) and from the M11 interchange to Thurrock (J27 to J30) in the north. The scheme also included refurbishment of the A1(M) Hatfield Tunnel (TL214083 to TL219093) to the north of J23 and the Bell Common Tunnel.
The scheme was completed by June 2012, in time for the London Olympic Games. The widening made good use of recycled materials, including at least 90 percent recycled aggregates.
Further works implemented under the DBFO concession, which remains in force until 2039, include Smart Motorway techniques between Sevenoaks and Merstham (J5 to J7) and South Mimms and the M11 interchange (J23 to J27), as well as a £55m upgrade of J30 at Thurrock. Smart schemes cover measures such as hard shoulder running and variable speed limits.
Tolls rates at the Dartford Crossing vary depending upon time of day and vehicle size. In 2015, the toll plazas were removed and a new safety system installed. The flexible Dart Charge is now collected electronically using number plate recognition, with travellers paying the relevant amount online, by phone or by opening an account.
In March 2016, the Department for Transport announced a new study to investigate improving the transport network between Wisley and the M40 interchange (J10 to J16) of the M25. The results are due by the end of 2016.
The Thurrock (J30) works are due to be completed in 2017-8. Future works planned to commence in 2019-20, include interchange improvements at Wisley (J10), Cheshunt (J25) and Passingford Bridge (J28) as well as upgrading to use Smart Motorway techniques between Wisley and the M40 (J10 to J16).
Contractors (listed in order of proportion of total project completed)
Laing, Balfour Beatty (constructed the first and last sections), Costain, Bovis, Fairclough, Sir Alfred McAlpine, Tarmac, Birse, A.E. Farr, Edmund Nuttall, W. & C. French, Wimpey, Gleeson, Cementation, Monk
Groundworks: C.A. Blackwell, E.J. Aldrich, John Jones
Research: ECPK
"London Orbital and M23 to Gatwick: Route Strategy", Highways England, Guildford, April 2015
"The M25 at 25", supplement to Transportation Professional, Chartered Institution of Highways & Transportation in association with Highways Agency, October 2011
"Review: Tomorrow’s London" review by John M. Hall, The Geographical Journal, Vol.136, Issue 3, pp.420-424, September 1970
reference sources   CEH Lond

M25 motorway (London Orbital)