Thorney Interchange from the south, looking north along the M25 in July 2009; it is junction 15 of the M25
|Type||4-level stack interchange|
|Constructed||by Cementation Company and Costain Group|
|Opened||19 December 1985|
|Maintained by||Highways England|
The Thorney Interchangeis a large motorway intersection in the UK, between the M4 and M25. It is one of the busiest motorway interchanges in the UK. It is situated directly on the edge of Buckinghamshire, Greater London (London Borough of Hillingdon) and Berkshire. It is also not too far from Surrey and Staines-upon-Thames.
The M4 (London-South Wales Motorway) under the interchange was opened in December 1964, from junctions 4 (A408) to 5; this 3.9-mile section cost £3.2m, and was built by Cubitts and Green. The interchange, hence, is junction 4b of the M4.
The interchange is around one mile north-west of Heathrow Airport; the interchange is the main junction for traffic heading from the M25 to the airport. The interchange is the point that the M4 enters Greater London.
The bridge decks were to be built of prestressed concrete, but instead were built with composite steel beams and concrete decks, designed to BS 5400. In the early 1980s, when the interchange was being built, the entire M25 was to cost around £600m.
The southern part of the M4/M25 interchange was part of a 2.05-mile section of the M25 which was due to open in spring 1985, the Poyle to Thorney Mill Road section, from junction 14 (Poyle Interchange) to junction 15. The £44m contract, given to the joint venture of Cementation/Costain, was to take three years.The M25 section was due to be open nine months before the M4/M25 interchange would open.
The northern section of the interchange was to be part of a 10.5-mile section of the M25 also due to open in spring 1985; this later became the 4-mile M4 to Iver Heath section to the M40, at Denham Interchange junction 16. The 6.5-mile section of the M25 directly north of the M40 opened in January 1985.
Much of the M25 was designed by Halcrow Group. The interchange was designed by Atkins.
3.5m cubic metres of infill was needed for the contoured landscaping.
The section of M25 to the north began construction in April 1983.Construction took 28 months, and cost £25m, with £10m for the fifteen bridges, by Wimpey Construction. The bridges were built to allow expansion to four lanes at a later date. The M25 was opened by Nicholas Ridley, Baron Ridley of Liddesdale on Wednesday 18 September 1985, an 11-mile section directly south of the M40 to Poyle. The section had cost £80m. The M4/M25 junction was planned to open at a later date of June 1986, but it opened six months early, due to good weather, on Thursday 19 December 1985. At the time of opening two sections of the M25 remained – in Hertfordshire and Kent (which opened in February 1986), and the M4/M25 junction was expected to be the busiest motorway junction in the UK.
It is a typical stack interchange. The part of the interchange that is north of the M4 is in Iver, in South Bucks. It is named after Thorney, Buckinghamshire, now part of Iver, the village in which the northern part of the interchange in situated. The part of the interchange that is south of the M4 is in Colnbrook with Poyle, in Slough. West Drayton and Harmondsworth are close to the east.
There are 11 bridges and three major viaducts, varying from 182m to 264m long. A 229m viaduct carries the M25 over the M4.
A single-track disused railway line passes through the middle of the interchange. The railway line, the former Staines and West Drayton Railway, is still there.The railway line went from West Drayton railway station, to the north, to Staines West railway station, to the south, and the disused section passes through the Lakeside Road Industrial Estate to the south.
The M25 or London Orbital Motorway is a major road encircling almost all of Greater London, England. The Dartford Crossing (A282) is part of the orbital route but is not part of the motorway. The M25 is one of the most important roads in Britain and one of the busiest. The final section was opened by the Prime Minister Margaret Thatcher in 1986; on opening it was the longest ring road in Europe at 117 miles (188 km).
Colnbrook is a village in the unitary authority of Slough in Berkshire, England. It lies within the historic boundaries of Buckinghamshire, and straddles two distributaries of the Colne, the Colne Brook and Wraysbury River. These two streams have their confluence just to the southeast of the village. Colnbrook is centred 3 miles (4.8 km) southeast of Slough, 3.5 miles (5.6 km) east of Windsor, and 18 miles (29 km) west of central London.
The M1 motorway connects London to Leeds, where it joins the A1(M) near Aberford, to connect to Newcastle. It was the first inter-urban motorway to be completed in the UK; the first motorway in the country was the Preston By-pass, which later became part of the M6.
The M4, a motorway in the United Kingdom running from west London to southwest Wales, was originally referred to as the London-South Wales Motorway. The English section to the Severn Bridge was constructed between 1961 and 1971; the Welsh element was completed in 1993. The construction of the Second Severn Crossing, officially renamed the Prince of Wales Bridge and inaugurated on 5 June 1996 by the Prince of Wales, caused the M4 to be rerouted.
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The M5 is a motorway in the UK linking the Midlands with South West England. It runs from junction 8 of the M6 at West Bromwich near Birmingham to Exeter in Devon. Heading southwest, the M5 runs east of West Bromwich and west of Birmingham through Sandwell Valley. It continues past Bromsgrove, Droitwich Spa, Worcester, Tewkesbury, Cheltenham, Gloucester, Bristol, Weston-super-Mare, Bridgwater, Taunton, terminating at junction 31 for Exeter. Congestion on the section south of the M4 is common during the summer holidays, on Friday afternoons and bank holidays.
The M18 is a motorway in Yorkshire, England. It runs from the east of Rotherham to Goole and is approximately 26 miles (42 km) long. A section of the road forms part of the unsigned Euroroute E13.
The M20 is a motorway in Kent, England. It follows on from the A20 at Swanley, meeting the M25, and continuing on to Folkestone, providing a link to the Channel Tunnel and the ports at Dover. It is 50.6 miles (81.4 km) long. Although not signposted in England, this road is part of the European route E15.
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Poyle is a largely industrial and agricultural area in the unitary authority of Slough, in the ceremonial county of Berkshire, England. It is located 18 miles (29 km) west of Charing Cross in London and immediately west of the M25 motorway, near Heathrow Airport; it also adjoins the Colne Valley regional park.
The Colne is a river in England which is a tributary of the River Thames. Just over half its course is in south Hertfordshire. Downstream, the Colne is the boundary between Buckinghamshire and London and finally between corners of Berkshire and Surrey. On leaving Hertfordshire, the watercourse splits off into several separate branches, a few of which rejoin it, and its main branch flows into the River Thames on the reach above Penton Hook Lock at Staines-upon-Thames.
The M63 motorway was a major road in the United Kingdom. It was completely renumbered as part of the M60 motorway in 1999 which orbits part of Greater Manchester.
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North Cross Route (NCR) was a planned motorway-standard road which would have formed the northern section of Ringway 1 and would have formed the innermost circuit of the London Ringways network. The six-lane dual carriageway with grade separated junctions to an extended M1 Motorway was planned during the late 1960s along with the rest of the Ringway scheme. It was never constructed due to large-scale opposition from many quarters.
The Staines & West Drayton Railway (S&WDR) is a former railway on the western edge of London, England. It was about 5 1⁄2 miles (9 km) long and ran roughly north-south along the River Colne, parallel to the modern M25 motorway west of Heathrow Airport. It opened from West Drayton on the Great Western Main Line to Colnbrook in 1884 and reached Staines the next year.
Poyle for Stanwell Moor Halt railway station was on the outskirts of London, on the now closed line of the Staines and West Drayton Railway.
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