Information AboutM4 Motorway |
The M4 motorway is a Motorway in Great Britain linking London with Wales . It is part of the unsigned European Route E30 . Other major places directly accessible from M4 junctions are Reading , Swindon , Bristol , Newport , Cardiff and Swansea . The M4 runs close to the A4 from London to Bristol. After crossing the River Severn it follows the A48 through Wales , until its termination just north of Pontarddulais. SPECIAL FEATURES ( England ) between junctions 19 and 20, looking west towards Wales .]] The elevated section in West London, built in the 1960s, is mostly directly above the A4 and extends over parts of Brentford 's Golden Mile . This section has a heated road surface to reduce icing in winter. The motorway is the only one in the UK to feature a 'dual-numbered' junction. Junction '8/9' is the turn off for Maidenhead , Berkshire . It has two of only three four-level Stack Interchange s in the UK, including the first UK example at the junction with the M5 (J20/" Almondsbury Interchange ") and the other at the junction with the M25 (J4B). Both are impressive feats of engineering, particularly junction 4B which also has to make provision for a railway line passing beneath the M4. However, due to the nature of such junctions, drivers should bear in mind that it is impossible to make a U-turn at J20 or J4B. The M4 Crosses the River Severn via a Toll Bridge , the second of only two on the UK motorway network — the first was the original Severn Bridge (the original route of the M4, now the M48 ). There is a special slip road west of the A34 to Newbury from the eastbound carriageway which leads to RAF Welford . This slip road is signposted in red lettering (the normal military signing standard), "Works Unit Only". Near Junction 35, there is a stretch of the motorway that has a surfacing of porous Asphalt that improves drainage and reduces noise. When driving in heavy rain conditions drivers notice a reduction in spray from other vehicles and improved visibility. This special surface was publicised in an episode of the BBCs Tomorrow's World programme. This was the site of the first trial of the new road surface when it was laid down in 1993http://www.hanson.biz/files/pdf/magazine/2006/2006Q4_op.pdf. NOTABLE JUNCTIONS Junction 27 at High Cross is a normal roundabout B-road junction, however the slip roads point in the wrong direction to the destination. Due to the topology of the landscape, both sets of sliproads are conjoined on opposite sides of the roundabout. To go to Cardiff, the driver must use an eastbound-facing sliproad before looping around 180 degrees to join the westbound carriageway. During the construction of the section around Cardiff in 1980, junction numbers were set aside for intermediate interchanges that were not built at the time. 33 had been set for the link road to the west ( A4232 ), 32 for the A470 , with 31 intended for the A469 to Caerphilly , and 30 for the great "Hook Road" - a plan which was later shelved. Junction 30 was later added to serve the A4232 Link Road , in the east, which will eventually form a Ring Road from junctions 33 to 30, via Cardiff Bay . Number 31 remains unused as of 2006, and there are no immediate plans to build a junction with the A469. Contrary to popular belief, junction 39 ''does'' exist. However, it consists of a single slip road completing the missing movement onto the westbound carriageway from the A48 at junction 38, thus there is no exit from the motorway at this junction. Junction 41 refers to two different junctions in two different directions, their movements not complementary. In the westbound direction, 41 is indicated as a spur leading to the roundabout in Briton Ferry formerly known as 41A, and the original bridge over the River Neath , which would allow access onto the stretch of the M4 from junction 43 westward. In the eastbound direction, 41 is indicated as an exit-only route to the A48 towards Port Talbot. As a result, it is possible in both directions to travel almost 2 miles (3 km) in the same direction having both joined and subsequently left the motorway at "junction 41". SPEED CHECKS from England to Wales on a Cable-stayed Bridge (the Second Severn Crossing ). Wales is seen in the distance.]]
Traffic heading into London travels at a maximum speed of 60 mph (97 km/h) after the Heathrow turnoff, the limit is enforced by Cameras . The elevated section is also enforced by speed cameras at 40 mph (64 km/h). Traffic heading out of London is limited to 40 mph (64 km/h) on the elevated section, but there are no cameras. Speed checks are also carried out by mobile Safety Camera Partnership vans on the toll plaza on the Welsh side of the M4 after the Second Severn Bridge. The speed limit is reduced to 50 mph (80 km/h) when approaching the toll plaza, and then raised back to the National Speed Limit after leaving the toll plaza. There are also mobile camera vans on sections of the M4 between the toll plaza and Cardiff. Between Junction 34 and Junction 37, there are three bridges crossing over the motorway. These three bridges sometimes have mobile speed camera vans parked on them to catch speeding motorists on the motorway below. These bridges are located on fairly sharp bends in the motorway.
DEVELOPMENTS As of spring 2007, the stretch between Junction 29 Castleton and J32 Coryton is being widened to 6 lanes in order to relieve congestion that plagues this stretch. Work is expected to be completed by December 2009 www.m4widening29to32.com . Plans are progressing for the M4 Toll Newport bypass, scheduled for completion by 2014.
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