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Opinion

Would a relief road resolve traffic problems on the M4?

12 May 2024 4 minute read
The M4 in Wales

Mike HedgesMS for Swansea East

The M4 is the major route between south Wales and London. It is important to both our economy and our movement for social reasons, but certain sections are often clogged at peak times.

I drove to Newbury and London last month which gave me an understanding of the road beyond my twice weekly journey to Cardiff and occasional journeys to other places on the M4 between the Pont Abraham service station and Newport.

The first 124 miles between London and Wales has twenty-eight junctions whilst the next seventy-eight miles in Wales has twenty-seven junctions. It is obvious that the average distance between junctions is longer in England than in Wales.

There are certain areas in Wales that have many junctions close together including seven around Newport over eleven miles. There are also five between the A48 for Port Talbot and the A48 at Briton Ferry a distance of six miles.

There are five between the A48 at east Swansea and Pontardulais a distance of nine miles.

Junctions

Many drivers use the M4 to travel one or two junctions to avoid using local roads. This is not a criticism of such drivers I use the M4 to go from my house to Penlan and to Birchgrove.

Is this what the M4 is for? Do we want it to be used as a local road around Swansea, Port Talbot, and Newport?

In England there are three Reading turn off within eight miles and in Bristol three junctions within nine miles.

There regularly traffic problems on the M4, as anyone who listens to radio Wales will know the three areas that have almost daily traffic problems are the M4 around Newport, M4 around Port Talbot, and the M4 around Swansea.

Problems

Except following accidents, there are rarely traffic problems between junction thirty-eight and junction twenty-eight. This excludes queues on the slip road at junction thirty-three and on entering the roundabout at junction thirty-two.

Are there solutions to these bottle necks? It has been suggested that an M4 relief road would solve the problem around Newport. That it would do serious environmental damage to the Gwent levels is without challenge, but would it work?

Around London the M25 was created as a motorway encircling most of Greater London to solve traffic problems. The 117-mile motorway is one of the most important roads in the UK and one of the busiest and has been described as the largest car park in the UK.

The M25 was originally built mostly as a three-lane motorway but much has since been widened to four lanes, to a five-lanes section between junctions 12 and 14 and a six-lane section between junctions 14 and 15. Twelve lanes between junction 12 and 14 is twice the size of the original road that was built.

A report in The Economist  after it was built said “it had taken 70 years to plan the motorway, 12 to build it and just one to find it was inadequate”.

Traffic levels quickly exceeded the maximum design capacity. The M25 has been criticised for having too many junctions with fourteen of them serving only local roads. Drivers who only use the M25 to travel a short distance are believed by some to have less overall driving experience, exacerbating traffic and safety issues.

What has happened around the M25 is major house building including The Bowmans Cross development near junction twenty-two that could see as many as 14,000 people living there. Substantial commercial development has also been built around the M25 including at Purfleet, within half a mile of Junction 31 of the M25, that provides 343,281 sq. ft of highly specified industrial and logistics space.

It is inconceivable that such developments will not, albeit on a smaller scale, happen around any M4 relief road. The answer to M4 congestion as Edwina Hart, the former cabinet member started to address, is to reduce the number of junctions. Closing junctions is unpopular with local people who use them, and the junction closed around Port Talbot was re opened after its trial closure.

We have two options – the first is to complain about the traffic problems, the second is to act, reducing the number of junctions on the M4 and see if that speeds traffic.

Finally, when is the M4 going to be completed to Fishguard?


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David Smith
David Smith
2 days ago

Thanks Mike. As you know, some major cities in S E Asia operate a colour coding system to reduce congestion, by preventing cars use on one day a week. Could that be another option?

Another Richard
Another Richard
2 days ago
Reply to  David Smith

No. Utterly unworkable without a degree of social control that would make the fuss over 20mph zones look trivial. Also, what if a hospital appointment falls on the day you can’t drive your car?

karl
karl
2 days ago

No it would fail. Because it would increase growth in car ownership. The same ownership that is starting to destroy terraced streets wit hso many cars there is little room to move. We need different

Dai Rob
Dai Rob
2 days ago

Good article, however……when they closed the M4 junctions around P.T. it caused complete chaos in PT….the town ground to a complete halt…..all the shops started to shut at 3.00, as everyone left early to avoid the chaos. Business were threatening to pull out of the town, the indoor shopping centre said it would close if the trial continued.
We had to M4 ploughing right thru the middle of our town, but we were not allowed to use it!

A far better idea, lets close all the junctions around Cardiff & Swansea!!!

mike hedges
mike hedges
1 day ago
Reply to  Dai Rob

Junction 29 around Cardiff has never been completed.

Rhys Jones j
Rhys Jones j
2 days ago

Can I point out the problem with the Bryn Glas tunnel isn’t the volume of traffic, once you get past Bristol and onto the bridge the traffic flows freely even at rush hour, there isn’t tons of traffic joining from the magor junction. The traffic is from the fact it’s going from 3 lanes to 2. Shut a lane anywhere on a motorway and it’ll cause traffic as you see with the relentless M4 road works, Wales has just decided to do it permanently… Twice. Also the M25 is such a mess because it was botched together. It was designed… Read more »

Stephen Price
Admin
2 days ago
Reply to  Rhys Jones j

Spot on.. and the 50mph speed limit on a motorway was another genius idea!

Howie
Howie
6 minutes ago
Reply to  Rhys Jones j

Unlike Reading and Bristol, Bryn Glas is only short hop to city centre hence it’s use by more local traffic.

Shan Morgain
Shan Morgain
2 days ago

All very well to speak of closing Junctions. The theory works. But I note the article carefully avoids suggesting which junctions to close.

hdavies15
hdavies15
2 days ago

Extending the M4 to Fishguard ? You must be joking. Good idea but not likely given that the Bay regime is predisposed to inhibiting travel rather than enabling it.

Neil Anderson
Neil Anderson
2 days ago

The Welsh Government’s case for the M4 ‘relief’ road was always risible and was never going to work. Especially at a maximum speed limit of 50mi/h (for air quality reasons), the road would quickly become as congested as the M4. Building more roads has never defeated congestion. ‘Roads to prosperity’? The most roads in the UK are found in the economically most deprived areas! Highways (like foreign-owned energy production) suck money out of Cymru and into England, Europe and Asia. At the heart of our ‘traffic problems’ are two inescapable facts – 1. there are just too many vehicles and… Read more »

Shan Morgain
Shan Morgain
2 days ago
Reply to  Neil Anderson

Excellent analysis. Thank you.

Ap Kenneth
Ap Kenneth
1 day ago
Reply to  Shan Morgain

“Electric cars do provide a more efficient power train but are used as inefficiently as petrol and diesel vehicles. The resource requirements (lithium etc) are just as destructive. The overall environmental cost is about the same.” Obviously any mining of any sort has associated problems, but minerals needed for batteries are miniscule in comparison with fossil fuels. A battery should now last half a million miles and the materials are reusable, while a tank of petrol or diesel gets you a few hundred miles and goes up in smoke and can never be used again and as a by product… Read more »

A Evans
A Evans
1 day ago

Typical bull*hit to justify wasting £millions on a relief road which was dismissed out of hand by Drakeford! Yet stretches of the Welsh M4, with few junctions are under 50mph limits. This slowing down traffic OBVIOUSLY leads to a build up of congestion!

Neil Anderson
Neil Anderson
1 day ago
Reply to  A Evans

Not so obviously, A Evans… First, a highway with a posted speed limit of 70mi/h will achieve mean speeds of 80 – 85% of that. Second, maximum flows are not achieved at maximum speed (say, 70); lower speeds (and depending on the characteristics of the road) will increase those flow rates. Optimal speeds to maximise flow will be about 50. That is why in variable speed areas, the speed is reduced to clear congestion. Third, the 50 limit is often imposed to improve air quality, say, the A470 beside Pontypridd. Finally, best be a few minutes late in this world… Read more »

Howie
Howie
1 minute ago
Reply to  A Evans

On the HoV roads from Abergavenny to Brynmawr which is 50mph, most days in daytime when I use it I am the only vehicle on it. Very little pollution.

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