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M25- The Road to Hell?
The M25 is London’s outermost ring road, an orbital motorway, whose 121.5 mile/195.5km circumference completely encircles the capital. The Motorway is not a true circle however, as a small stretch of non-motorway A282 joins both ends of the M25 on the East side of London either side of the Thames crossing. The motorway attracts up to 200’000 vehicles per day and is widely considered the busiest motorway in Europe. It is also the largest ring road in the world.
The motorway begins at the south approach to the Dartford crossing, at junction 1A. It runs southwest from there and largely follows the Greater London Boundary. The only place within this boundary that lies outside of the M25 is North Ockendon, just south of junction 29 on the East side of London. The Mayor of London, Ken Livingstone, has argued for the uniforming of the Greater London boundary entirely to the M25. The M25’s greatest radius from central London is 20 miles (1).
Ideas for a London ring road were first discussed at the start of the 20th century, with basic designs appearing as early as 1911 (2). In 1935 two famous British architects, Lutyens and Bressey, put forward a plan but when nothing had materialised by 1939, the scheme was considered unfeasible due to the hindrance the war would cause. By 1943 the end of the war drew near and another great British architect was hired to effectively recreate London. Patrick Abercrombie included within his second scheme, the ‘Greater London Regional Plan’ of 1944, the design of five separate ring roads around London, although this was later reduced to an inner ring, comprising the north and south circular roads, and an outer ring, the M25 (3). This became known as the ‘Greater London Development Plan’.
The Dartford crossing of the Thames lies on the east side of London between Dartford and West Thurrock. Although not actually part of the M25, this was the first piece of the scheme to be constructed. Build began in 1957 with the north approach, and was completed and opened to the public in 1963. The crossing originally consisted of one tunnel, housing dual lane two way traffic, however the volume of traffic this would allow was quickly considered insufficient. Therefore in 1980, while construction of the M25 was still underway, a second tunnel was introduced allowing twin lane traffic in each direction. Being that this is the only Thames crossing after Woolwich (approximately 7.5 miles/12km away); the decision was made during the design of the M25 for the Dartford crossing to remain an ‘A’ road, still allowing non-motorway traffic to cross.
Because each piece of the motorway had to pass statutory standards on its own individual merit, a total of 37 contracts were issued for the construction, also meaning that no logical order was achieved upon creation. Prior to, and during construction, 39 public inquiries were held before independent inspectors. These inquiries lasted in total 700 sitting days, over a period of several years (4).
The route of the M25 obviously had to provide vital links to major motorways such as the M1 and M4, as well as roads going in to central London. With these criteria met, the route was largely governed by aesthetics.
Just under half of the southerly route of the M25 passes through Areas of Outstanding Natural Beauty, meaning that although this was essentially a city route, great care and attention had to be paid to sitting the motorway discretely and unobtrusively into the landscape. An example of this being the large earth mounds put in place parallel to the motorway for a large part of the distance between junctions 3 and 5, in order to disguise it from the river Darenth just a mile or so east of the motorway. Also, between Reigate and Leatherhead in the south east of London the foundations were laid lower than the optimum engineering level so the motorway is largely unnoticeable to nearby residents, both in terms of sight and sound.
A problem was encountered when negotiating the route through the north east quadrant. This is partly due to the dense residential and industrial building in the Waltham Cross area, and the obvious but unenviable task of passing this major motorway through the northern tip of Epping Forest. The solution that emerged came in the form of tunnels in both cases. Both sections were built to motorway standard and then ‘lids’ were built above them. The Bell Common tunnel in Epping is 470 metres in length, while the Holmesdale tunnel at Waltham Cross is 650 metres in length, this tunnel incorporates the use of water pumps in the tunnel roof, ensuring proper drainage. This was not needed at Epping, as gravity does the job suitably. A special act was needed to allow the passing of the forest in this way and large embankments were placed either side of the motorway for approximately half the distance between junctions 25 and 27, again for visual and acoustic purposes. 20’000 trees have been planted along every mile of the motorway, another measure to compensate damage to the landscape (5).
There are two main types of highway construction, that of rigid construction, and that of flexible construction, whereby the flexible highway may experience slight vertical deformation at the surface whilst still retaining its structural integrity. The M25 consists of approximately 46% rigid pavement and 54% flexible (6).
The pavement construction consists of five primary layers - the subgrade, capping, subbase, roadbase and surfacing. The subgrade is the layer of soil exposed when excavating the path of the motorway. It is often bound by either lime or cement to provide maximum stability for the capping. The soil is tested for its drainage properties, responses to freezing, and content of chemicals damaging to any of the stabilizing materials or binders. The capping layer consists of cheaper materials than the upper layers, often crushed concrete. The subbase consists of either unbound granular material, such as soil, or cement bound fine aggregate. This varies between rigid and flexible parts of the pavement, flexible pavements generally making use of the former. The roadbase is the main load distributor, ensuring that large forces aren’t exerted on the subgrade, minimising low level deformation. In the case of the M25 the roadbase is entirely cement bound, as it experiences massive loads each day. The base course which is then applied on the roadbase consists of graded aggregate (typically crushed rocks no larger in diameter than 20mm). The surface of the motorway is asphalt concrete, and provides all the necessary properties for a heavily trafficked road. Asphalt is a type of bitumen, a binding liquid similar to tar, derived in a number of ways from crude oil. This is then heated and mixed with a mineral aggregate before being laid. Obviously the surface of the M25 has been updated in some parts during numerous widening schemes.
The overall construction included 260 bridges over or under the M25. One of which was the Queen Elizabeth II Bridge next to the Dartford tunnel, allowing for 4 lane traffic in each direction across the Thames. The cable stayed bridge was designed by Sir William Halcrow & Partners and was opened to traffic in 1991. The new Haw viaduct in Byfleet, in the south east quadrant, was built to discretely pass over the river Wey navigation canal, and the London – Southampton/Portsmouth railway line. The viaduct consists of 14 parallel concrete pillars supporting the motorway above the canal, and two separate pillars to include the railway. This is a good example of the designers and engineers striving to set the motorway suitably into the landscape (7).
Figure 1, attached, is a table displaying the chronological order of construction of the various sections of the M25.
The final section of the motorway from junction 19 in Micklefield, to junction 23 in South Mimms, was opened to the public by Margaret Thatcher in October 1986. The road was immediately considered incapable of carrying the volume of traffic it was attracting, completely contradicting initial concerns that no motorway was needed at all. One reason for the unexpected volume of traffic is the numerous amounts of junctions. The motorway is considered to be a link to major routes, but many local people also make use of it for short distance journeys. Another reason is that somehow the demand for the road was massively underestimated, despite lots of research.
The majority of the M25 today is still six lanes wide, although a small part is four lane, approximately one sixth is eight lane, and schemes are underway at the moment between junctions 12 and 14, and junctions 14 and 15 to widen them to 10 and 12 lanes respectively (8).
By 1986 the bill had reached £909m, making it Britain’s most expensive motorway, and the lack of capacity spelled even more costs (9). However, the encouragement of economic growth both within and outside of London that this motorway provided is massive, and due to the links it has made, it is blatantly one of the most important examples of civil engineering in the UK. I think this is far too often taken for granted, as it is perhaps not one of the most obvious candidates, probably mainly down to the fact that so many of us use it on a regular basis, and it is likely considered subconsciously as part of the landscape. If anyone was to spend just a short time looking into where the M25 actually came from, they would see a wealth of history, inclusive of many different civil engineering disciplines, at different stages throughout the 20th century. I do not believe this is the road to hell, merely an underestimated yet massively significant construction that due to incorrect assumptions made at an early stage will be trying catch up with demand for a large part of its life.
www.sabre-roads.org.uk – Sabre road forums provided figures for (1), (3)
en.wikipedia.org – Wikipedia provided figures for (2), (8)
www.ukmotorwayarchive.org.uk – UK Motorway Archive provided figures for (6), (7)
www.cbrd.co.uk – CBRD provided figures for (4), (9)
www.highways.co.uk - Highways agency provided figures for (5)
Highway Construction and Maintenance, 2nd Edition, by John Watson
UK Motorway archive M25 archives – www.ukmotorwayarchive.org
Sabre Roads – www.sabre-roads.org.uk
Here are all the non D3M bits:dartanian wrote:Just wondered.......where is the four lane bit ?
Part of the A282 near the crossing - D4H
From J6/7 (A22/M23) to J16 (M40) - D4M
J21a - J21 (through the M1 junction) - D2M
J27 (through the M11 junction) - D2M
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except it's D3M through j10, 11, 12 and 15. and also is D5M between j12 and j13, j13 and j14 (with a short bit of D6M extended slip near j14) and, supposidly as of very very soon, fully open D6M between j14 and j15!MSAJohnny wrote:From J6/7 (A22/M23) to J16 (M40) - D4M
There must be some advantages to why approximately half the M25 was of rigid pavement?daesson wrote:..rigid construction, and that of flexible construction, whereby the flexible highway may experience slight vertical deformation at the surface whilst still retaining its structural integrity. The M25 consists of approximately 46% rigid pavement and 54% flexible (6).
Unbound sub-base (type 1) is generally produced from crushed rock not soil.daesson wrote:......The subbase consists of either unbound granular material, such as soil, or cement bound fine aggregate. This varies between rigid and flexible parts of the pavement, flexible pavements generally making use of the former. ... In the case of the M25 the roadbase is entirely cement bound, as it experiences massive loads each day. The base course ... consists of graded aggregate (typically crushed rocks no larger in diameter than 20mm). The surface of the motorway is asphalt concrete, and provides all the necessary properties for a heavily trafficked road.
The roadbase on the M25 is not entirely cement bound. In the rigid areas there is no roadbase, in the flexible areas it may be either cement bound or flexible. Asphalt concrete is a term not generally used. It is better to refer to hot rolled asphalt which still makes up the majority of the flexible surface.
It would be better to call these piers or columns.daesson wrote:..14 parallel concrete pillars supporting the motorway above the canal, and two separate pillars to include the railway.
You could include a paragraph about current government policy to not cater for this demand in widening schemes by provision of alternatives such as HOV lanes .daesson wrote:.... will be trying catch up with demand for a large part of its life.
Hope this helps
It's worthy of its own page (and site!) but a home can always be found for waifs and strays on the RD. I've linked to this thread from the RD entry on the M25.A68Nick wrote:Good effort! I think that's the sort of thing we should archive somewhere (with the author's permission) like CBRD, etc.
Yes. The Holmsdale tunnel is shortly due for an upgrade, and works have taken place to strengthen the surrounding roads to cope with the diverted traffic whilst work takes place.ndp wrote:Isn't the M25 currently 2 lanes in one direction, 3 in the other through the A10 junction?
Is the 2 lane section going to be upgraded to 3 lanes or is something simpler such as resurfacing happening?gazza72 wrote:Yes. The Holmsdale tunnel is shortly due for an upgrade, and works have taken place to strengthen the surrounding roads to cope with the diverted traffic whilst work takes place.ndp wrote:Isn't the M25 currently 2 lanes in one direction, 3 in the other through the A10 junction?
What does that make roads that should be motorway, for instance the A27 between the M27 and A3(M)?Lewis wrote:I would say the A282 is D4M as it has a full width hard shoulder, making it physically a motorway, however, legally it is not.
My understanding of these abbreviations was that they described the physical nature of the road.
And what about motorways w/ no hard shoulder, like the A57(M)?
Sorry, wasn't thinking, should of put D4H.Lewis wrote:I would say the A282 is D4M as it has a full width hard shoulder, making it physically a motorway, however, legally it is not.
My understanding of these abbreviations was that they described the physical nature of the road.