It is loved and hated in equal measure. It is possibly Europe's most notorious ring road. Yet without it, most of Greater London would be considerably more congested than it is today.

The M25 is a 117 mile long orbital motorway that encircles the capital, carrying almost 200,000 vehicles along its busiest section near Heathrow Airport. Yet its origins are somewhat complex...

 

Bypassing London

The advent of the car saw almost immediate calls for an orbital route to be constructed around the capital. By 1905, it was seen as unacceptable that such a scheme was not actively being considered. Rees Jeffreys from the Royal Commission on London Transport said, "it was a disgrace that no road existed which encircled the English capital city" and that there was an "urgent need" for such a route.

The result was the construction of the North and South Circular Roads, which started in 1911 but was only completed in 1935 due to the piecemeal joining together of suburban routes to create the South Circular.

Despite this, politicians were already demanding an orbital route be constructed some 12 miles away from Central London. Initial plans for what would be known as the North and South Orbital Roads were drawn up during the 1920s, and some northern sections even got as far as being built.

More coherent plans were published in 1938 following a comprehensive study by Ministry of Transport engineer Sir Charles Bressey and consultant Sir Edward Lutyens. Taking a close look at traffic speeds on roads within the London area, they were able to see the effectiveness of orbital routes when compared to radial routes. It was found that the 12.5mph average speed on radial routes dramatically improved to 23.5mph on the North Circular.

Six years later and another set of proposals emerged. This time London's Chief Engineer, Sir Patrick Abercombie, came up with a radical scheme for five orbital routes comprising of a mixture of motorways and arterial dual carriageways.

These plans included the North and South Orbitals, but were deemed to be too far out to provide any relief to London's congested roads. Instead, this road - known as the "E Ring" would be a simple dual carriageway road with level junctions, whilst the main outer orbital motorway (the "D Ring") would be built slightly further in. The only significant change was a different alignment on the eastern side of the route.

Again, nothing came out of these proposals and so another set of plans were drawn up during the 1960s. Known as the Ringways Scheme, this plan would make attempts to stop the deteriorating traffic conditions within London. Four high-quality roads were proposed, based on Abercombie's earlier idea; the outermost route of these would be Ringway 4, which would mainly incorporate the earlier E Ring.

However, it wouldn't be a complete ring - south of London, it would merge with the planned London to Dover motorway at Wrotham Heath, whilst north of the Thames, it would terminate on Ringway 3, which took over the Brentwood - Dartford section of the North Orbital Road.

Despite the ambitiousness of the scheme, the Ringways project was met with very fierce opposition from a number of groups. Despite attempts to change the plans to appease those who wanted to see it cancelled, the Ringways suffered that fate in 1973. It looked like an outer orbital route for London may never see the light of day.

 

Joining the dots

Something had to be done. London was getting busier and busy by the day, and the increasing popularity of the private car meant that the road network was saturated. The North and South Circular roads were not able to provide the function of getting traffic across the Capital as they couldn't handle the amount of local and long-distance traffic using it.

Even though the Ringways had been cancelled, it was hoped that some parts of it would still be built. Three routes were planned, these being the North & South Circular, the northern part of Ringway 3 and most of Ringway 4.

The Hayes to Dartford part of Ringway 3 would be built as the M16, whilst Ringway 4 (the North and South Orbital) would be built to a mixture of standards - the Brentwood to Watford stretch would be built as a standard A-road, whilst the remainder of the route round to the M20 would be a motorway - the M25 was born...

Yet even that plan was quickly changed, with the government deciding only one orbital route would be built. The M16 and M25 would be merged into one route, with both routes losing bits to make them fit together. In the case of the M16, the Hayes to Watford section would be cancelled, whilst the non-motorway part of the North Orbital would be scrapped (despite a large part of it already existing).

As the M16 and M25 would finish on opposite sides of Watford, it was decided that the two stretches of motorway would need to be linked together; this is why the motorway has a "bump" around the north of Watford. A link would also be built from the South Orbital at Sevenoaks up to the southern end of the Dartford Crossing. The whole lot would be given the number M25, with the resulting stub of motorway east of Sevenoaks becoming the M26.

 

Building the orbital

Due to the complete motorway being 117 miles long, construction of the route was broken up into 41 separate contracts, covering various lengths, bridges, spurs and individual junctions.

Because of this, the time taken to build the entire motorway was 13 years. This was because each section was treated as a separate road, going through its own individual planning process. This led to 39 separate public inquiries being held, lasting a total of 700 sitting days.

Consequently, a number of sections were isolated from other stretches. To combat this, a few parts of the motorway opened as normal "all-purpose" roads, with motorway restrictions being imposed later when adjacent sections opened. There are also instances where the motorway took over parts of existing roads, an example being the stretch between junctions 22 and 23, which were originally part of the A6.

The large number of contracts meant that the road, once fully opened, constantly switched between "rigid" (concrete) and "flexible" (asphalt) surfacing. This was because the specification for all bar one of the contracts gave options for both types of road (the exception being rigid only for performance monitoring purposes).

A total of 46% of the road was built as rigid, involving 2,000,000 tonnes of concrete. The remaining 54% of the motorway was constructed with flexible surfacing, using 3,500,000 tonnes of "black top" asphalt. Over two million trees and shrubs were planted alongside the road as part of an extensive landscaping project.

 

A victim of its own success

The first stretch of M25 opened in September 1975, this being the section between junctions 23 to 24. However, it actually opened the A1178, only becoming a motorway when the adjacent section east of Potters Bar opened.

By the time the last section opened 11 years later on 29 October 1986, plans were already afoot to increase capacity on certain parts of the motorway. Over 100,000 vehicles were using some parts on a daily basis, and three lanes simply were not enough. It was only designed to carry 88,000 vehicles per day.

By 1990, the first proposals to widen the motorway to four lanes each way were announced by the Government, due to the continuing growth of traffic using the route - within three years the vehicle count had reached 200,000 vehicles per day.

There are some stretches of the motorway that are constantly struggling to meet demand 25 years after the motorway opened. Whereas 200,000 vehicles were using the motorway as a whole in 1993, that many vehicles are using the short section between the M4 and M40 (i.e. past Heathrow) alone today. So much so that this bit was widened from three to four lanes then to six lanes in 2005!

Capacity is still being added where possible, with most of the motorway being four lanes wide in each direction. The only part retaining its original three lanes configuration is between Junctions 3 (Swanley) and 5 (Sevenoaks) - however this may not be for long as plans to widen this are currently being considered.

 

Motorway Facts

Fully opened:	29 October 1986
Total length:	117 miles
Cost:	£909 million (1986 prices)
Tunnels:	2
Bridges:	234
Radius:	13 to 22 miles (from Charing Cross)
Busiest section:	Junctions 13 to 14
Daily traffic flow:	196,000 on busiest section

 

Bibliography

Highways Agency website
The Motorway Archive

 

Images on this page are copyright The Highways Agency.