M4 Junction 8/9

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The only dual numbered motorway junction in the UK.

Some info on this courtesy of this website;
www.iht.org/motorway/m4londswind.htm

A new route from London to South Wales was first envisaged in the 1930s, and proposals were drawn up for a series of local by-passes which could eventually be joined together to form a new route. The Berkshire County Council started to build a by-pass of Maidenhead, but work had to be abandoned in the early stages because of the outbreak of war in 1939.

After the war, the Special Roads Act 1949 gave highway authorities powers for the first time to provide roads restricted to certain classes of traffic, with access limited to a few specially constructed interchanges. The Minister of Transport decided that these powers should be used to provide the Maidenhead By-Pass, and the adjoining by-pass of Slough, as Trunk Road Motorways.

In 1956 the Government announced a plan for modernising the trunk road network based on five major projects, one of which was a road from London westwards to London Airport, the Bristol area and South Wales. The Maidenhead and Slough By-Passes were to be incorporated into this road, and construction of the Maidenhead By-Pass started again in 1959.

In 1960 the target of constructing 1,000 miles of motorway by the early 1970s was set. The London-South Wales Motorway was part of this 1,000 mile programme, and with the opening of the Maidenhead By-Pass in 1961 the first six miles of the M4 Motorway came into use.

Some six years later, in 1967, some 63 miles were open to traffic - 24 at the London end between Chiswick and Maidenhead Thicket, and about 39 at the western end between Tormarton in Gloucestershire and the Newport By-Pass in Wales. This western length included the Severn and Wye Bridges which were opened by Her Majesty the Queen in September 1966.

The 78-mile gap between Tormarton and the Maidenhead By-Pass remained to be filled. In June 1971 the gap began to close when 10½ miles between Tormarton and Stanton St Quintin were opened, and by November the motorway was extended another 18 miles eastwards to Badbury in Wiltshire, leaving only 50 miles to be completed. The opening of the 50 mile length between Badbury and Maidenhead By-Pass (Holyport) meant that there were 139 miles of continuous motorway between London and South Wales.

Planning the route

In January 1961 Sir Alexander Gibb & Partners were appointed as Consulting Engineers by the Minister of Transport to investigate and report on possible routes for the motorway. The terminal points were to be at Tormarton in Gloucestershire and on the Maidenhead By-Pass. The plan then existing (based on work done by the Berkshire and Wiltshire County Councils prior to the outbreak of war in 1939) was for a motorway keeping to the south of the Bath Road (A4) from Maidenhead to Chippenham, apart from a short length north of Calne, and then passing to the north of the Castle Combe valley. The lengths in Wiltshire and east of Reading were being protected from development by the local planning authorities.

At an early stage in the investigation it became evident that Reading and Swindon were the two focal points and that the protected route in Wiltshire should be abandoned. The route then recommended by the Consulting Engineers for the 30 miles eastwards from Tormarton to a point near Swindon has been adhered to ever since with only minor variations, but before a satisfactory route could be found for the 48 miles between Swindon and Holyport no less than 815 miles of routes were surveyed and studied. During these investigations there was much public concern about the possible routes for the motorway east of Swindon. One of the routes passed to the north of Swindon and followed the Vale of White Horse to two crossings of the River Thames near Wallingford and Henley. Another adhered close to the Bath Road (A4) between Maidenhead and Kintbury and known as the Direct Route, crossed the Thames at Shiplake and Streatley and proceeded almost due west, keeping to the north of Lambourn. This was the route initially preferred by the Minister, but changes were made to it to avoid most of the high downland and the Oxfordshire beechwoods. The concept was again re-examined to take account of possible developments arising from the Channel Tunnel project and the South East England traffic study, then recently completed. Finally, in August 1965, the Minister of Transport announced details of the selected route and between 1966 and 1968 draft Schemes under the Highways Act 1959 were published to establish the route between Tormarton and Holyport. After the consideration of objections the route was finally fixed with some minor modifications in August 1968.

Orders under the Highways Act 1959 also had to be made to authorise alterations to existing roads necessitated by the construction of the motorway, and nearly 50 miles of new side roads have been built along the 78 miles of motorway.

The route as constructed

The new Motorway leaves the Maidenhead By-Pass at Holyport, on a 19 mile section constructed by Costain Civil Engineering Ltd. At Winnersh a free flow junction and further work, built by W & C French (Construction) Ltd, ensured an easy access to Reading. The Motorway passes to the south with an interchange on the Reading-Basingstoke road and another on the A4 at Theale where a new by-pass will reduce the traffic in this severely overloaded village.

Junction 8/9 is also special in that it contains some of the very few traffic lights technically on a motorway and hence under motorway regulations.