Even today it’s a sobering thought that although the British motorway age dawned late in 1959 with the opening of  the first 67 mile section of the M1, completion of a motorway connecting the south Wales cities of Cardiff and Swansea was years away. 

The first part of it was just over four miles long, and opened in 1966, with only two lanes per carriageway, already – in general terms – well short of fast-evolving motorway design standards… by something close to a welsh country mile…

The full story behind this remarkable piece of road is now partly hidden by the veil of time, with key design paperwork now seemingly vanished. Yet enough words and pictures remain to piece together a remarkable story from an age when building new roads was rarely controversial – and usually welcomed with open arms. 

Historically the main road route linking south Wales with England was the A48, winding its way from Carmarthen through the centres of Swansea, Newport and Cardiff, before – in the absence of a Severn bridge – striking north to Gloucester. After the second world war, it was a recipe-in-waiting for almighty future traffic jams.

Plans for an already much needed bypass for the busy conurbations of Port Talbot and Aberavon were first commissioned from Architects and Engineers Sir Owen Williams and Partners in 1953. Traffic was rapidly increasing in the area, driven by continuing post-war growth in the Welsh coal, steel and manufacturing industries, and especially by the opening of the first Port Talbot steelworks in 1951. However, long before Welsh devolution, it was 1958 before the cash-strapped British government finally gave the go-ahead – around the time the M1 was being built. 

Public consultations were a token gesture in those distant days, so perhaps the public weren’t fully informed about the intended bypass route or the intrusive nature of the proposed design. Few objections to its construction seem to have surfaced, and statutory procedures were completed during 1962, with contracts for the work let soon afterwards. 

Seriously limited by the area’s topography, this was the first example in Britain of major new road construction slicing through the heart of an established, intensively built up, heavily populated area. Sir Owen and his team chose high-level, viaduct-style construction for much of the route, and engineering analysis in recent years has revealed much effort going into structural standardisation – to facilitate rapid and efficient construction. The design clearly draws on experience gained by Owen Williams’ partnership in rapidly constructing over a hundred semi-standardised bridges and related structures for the first M1 motorway. 

The elevated structure’s dominant feature is its very extensive use of concrete to carry a flat slab reinforced concrete road deck 14in (0.36m) deep. This accommodates two-and-a-bit traffic lanes in each direction, running continuously at high level on 45 ft (13.7m) columns, placed at 18 to 20 ft centres.(approx 5.8m) Where the road’s  interchanges required longer spans, columns were replaced by open concrete structures with top flanges cast integrally as part of the deck. At river crossings the piers are solid vertical slabs, but below ground they are hollow – reducing dead weight on the foundations.

The design was seen as state-of-the-art in its day, drawing sightseers from miles around. However its a measure of much changed attitudes to roadbuilding in the last 60 years that the significant social and community drawbacks of the chosen route – and the design’s major environmental impact – were virtually ignored. With a token public inquiry in 1953 followed by years of delay, property sales must have been blighted by uncertainty for a decade. Press reports suggest some efforts were made to minimise the impact of the construction work, but compulsory purchases forced many people to leave their homes, with over 200 houses demolished. 

Those continuing to live nearby faced years of disruptive construction work, ending in a situation that – given the height of the running carriageways – must have been extremely intrusive. This is a road that surely changed lives, right down to views from windows morphing from quiet streets of terraced houses into unremitting concrete columns and walls. Worse, this new alien environment brought an unwanted accompaniment: the endless drone of passing vehicles running on noisy concrete. Worse still, the Port Talbot bypass came 10 years before the 1973 Land Compensation act, so – no matter how bad the effect, or how noisy, close or intrusive the road proved, residents and communities received nothing in compensation. 

Yet newspapers of the day reported little campaigning to stop or divert the new road; reflecting benign public acceptance that it must be built, and was worth it to alleviate serious local traffic problems – whatever the cost. In the early 1960’s, though the social cost seemingly counted for little, by roadbuilding standards the financial cost was huge. At £5.06m for just over 4 miles – when ‘ordinary’ motorway cost around £250,000 per mile – the Port Talbot bypass simultaneously became the most expensive British road scheme of the day – in more ways than one – and a remarkable engineering feat, testament to the skills of Welsh grocer’s son Sir Owen William and his team. 

Initially numbered A48(M), it opened on 22 July 1966, on a route that would surely never have been considered today. It became part of the M4 in the mid 1970’s, and – though now a curious design relic from an entirely different age – most of it remains part of the M4 today. Somewhat ironically, the westernmost section – for so long the motorway terminus with the A48 at Baglan – was itself later bypassed, creating one of Britain’s longest motorway slip roads. Its replacement was the final missing M4 section, which connected Swansea to London in December 1994 – a stark reminder it had taken almost 30 years to complete this vital south Wales motorway link.


The full story of the building of the M4 from J32 as far as the end of the Port Talbot bypass can be found here:


Some limited original information relating to the building of the bypass is archived under reference MAWIM4/K41 (Groes to Baglan (Port Talbot Bypass) at the Glamorgan Record Office. The file is not available on line, but enquiries can be made via  http://glamarchives.gov.uk

Some facts about an interesting Port Talbot bypass junction are here


There is a remarkable gallery of historic photographs showing many aspects of the construction of the Port Talbot bypass, its route cutting through the heart of the built up area, and its remarkable proximity to houses, schools and other buildings along the way at this website:


There is also a piece on their Facebook page.

It’s not generally known but the Port Talbot bypass was unofficially opened by our chairman, Robin Roberts, and his father the day before the real event.Our chairman was with his father driving through the town and Mr Roberts Senior was looking for the road to Maesteg when he accidentally drove up a sliproad where the barriers had been removed for access by workmen.Within seconds their Ford Prefect was on the new motorway and had to dodge around local people who had taken the opportunity to view the town from over the barrier beside the road and walk their dogs, as workmen finished off painting and installing drain covers. Some 15 minutes later the intrepid two-some had emerged from the end of the new motorway and continued on their way as it rejoined the A48 at Baglan, to the startled look of construction workers at the other end. 
Dave Moss
Dave Moss

Dave Moss has a lifetime connection with the world of motoring. His father was a time-served skilled engineer from an age when car repairs really meant repairs: he ran his own garage from the 1930’s to the 60’s, while Mum was the boss’s secretary at a big Austin distributor. Both worked their entire lives in the motor trade, so if motor oil’s not in Dave’s blood, its surely a very close thing.

Though qualified in Electronics, for Dave it seemed a natural step into restoring a succession of classic cars, culminating in a variety of Minis. Writing and broadcasting about these, and a widening range of motoring matters ancient and modern, gathered pace in the 1970’s and has taken over since. Topics nowadays range across the modern motoring mainstream to the offbeat and more arcane aspects of motoring history, and outlets embrace books, websites national and international magazines, newspapers, radio programmes, phone-ins and guest appearances. Spare time: hard graft on the garage floor attending to vehicles old and new. Latest projects: that 1968 Mini Cooper S has finally moved again after 30 years, and when the paint is finished, the 1960 Morris Mini 850 will also soon be ready for the road again…

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