The M4 relief road in South Wales – will it be built and what will be the cost?

The Welsh Government is due to make a decision on whether to spend £1.4 billion to build a new motorway across the Gwent Levels to alleviate congestion on the M4. Many businesses and local people welcome the idea but conservation bodies point to the destruction of key wildlife habitats. Regular user of road and rail in South Wales Fergus Collins investigates the issue

Published: November 7th, 2018 at 10:48 am
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In October 2018 I crossed a sad, personal rubicon. It was when I decided that I could no longer commute by train from my home in Abergavenny to my work in Bristol. After six years of hard grind, the cost, overcrowding and complete unreliability of the train service between the major cities of Cardiff and Bristol had brought me close to a breakdown so it meant that I had two choices. Buy a cheap commuting car or move from my beloved Welsh hills back to the city.


I bought the commuting car (an editor of a rural magazine ought to live in the countryside) – something I had vowed never to do. But once I looked at the data, it made sense in most areas.

  • The car journey is 10-20 minutes quicker
  • I’ve worked out that I get 12.5 miles per litre – so about 8 litres of fuel for the 96-mile return journey = £10.60 (at current fuel prices) + £5.60 toll. Just 30p cheaper than the day return on the train (£16.40) but once the toll is removed on 17 December 2018, it becomes that much cheaper.
  • It’s more reliable and more comfortable.
  • It is probably more polluting than the train.

It appears the Welsh Government has taken the same view – proposing to invest in a new ‘relief’ road for the M4 from the ‘new’ Severn Bridge through the Gwent Levels and to the south of Newport. The aim is to alleviate pressure on a pinch point around the Brynglas Tunnels at Newport, where the current motorway drops from 6 to 4 lanes and causes tailbacks (which I have sat in on many occasions coming home in the evening).

The 'new' M4 bridge heading into Wales. Now known as the "Prince of Wales Bridge". Bridge tolls will be reduced to zero this December.

The Welsh Government told me that “the M4 Project would improve the economic performance and attractiveness of Wales as a place to do business, live and visit, helping to attract and retain skilled jobs and investment, with the cascading socio-economic benefits that brings to our communities both local to the scheme and further afield.” And that “The project would undoubtedly require a significant infrastructure investment but every £1 spent would return over £2 for Wales.”

It sounds like good news for motorists and for businesses in South Wales and this optimism is backed up in the comments sections of articles on the project on various online news sites for South Wales. But it is currently projected to cost £1.4 billion and not everyone is in favour – there is a powerful counter argument to building this new road.

Map courtesy of the BBC News website. The green line (actually called the 'Black Route' by the Welsh Government) shows the route through the northern Gwent Levels.

I visited Magor Marsh Nature Reserve on the Welsh side of the Severn, just to the south of the new bridge. Here I met Gemma Bodé from the Gwent Wildlife Trust (GWT), which manages much of the Gwent Levels for wildlife. She took me on a tour of the site and then a wider exploration of the Levels where we saw a host of bird and fish life, dragonflies, butterflies and an extraordinary range of plantlife among the ditches, rivers and water meadows. And there were pretty villages and farms hidden in the wetlands with distinct local architecture; historic churches and appealing country inns.

Magor Marsh in South East Wales – typical Gwent Levels habitat. The new M4 relief road will destroy a small part of this reserve but up to 5km of waterways throughout the rest of its route. Photo by Kim Louise

The Welsh Government claims that the M4 Project “would require less than 2% of the Gwent Levels Sites of Special Scientific Interest and the route has been located as far north as possible on the edges of them, with over half of it running on brownfield or contaminated land.”

Bodé disagrees and describes the Gwent Levels as “One of the most important floodplain grazing marshes and reedbed systems in the UK”, with nationally important numbers of water voles and wading birds – even breeding cranes. She revealed her fears for whole area should the relief road go ahead. “125 hectares would be lost including 5km of precious ditches, which hold the rarest wildlife.” Two acres of the northern end of Magor Marsh would also go under concrete.

Typical Gwent Levels waterway and grazing marsh habitat. Photo by Kim Louise

Bodé argues that this is just the latest scheme to threaten the Levels, with the city of Newport looming over the western edge and the hundreds of hectares lost to the steelworks within the last 50 years. In addition, Bode’s points to the extra pollution the road would inflict through the region.

I asked her how she would respond to those people living and working in South Wales who might benefit from quicker journey times. Is wildlife more important than people?

“Our natural world does a huge amount for us. These wetlands are a huge sponge and stop Newport and other towns from being flooded,” she says.

I put this to the Welsh Government whose spokesperson replied: “Potential negative impacts on the Gwent Levels and its SSSIs have been carefully considered. The route of the road skirts the northern edge of the SSSIs, with over half on brownfield land. Ecology teams would carefully create new ecological habitats and over 110 hectares of new woodland would be planted. Innovation has been integral, with water treatment using natural reed beds and a 440m span cable stay bridge designed to avoid any impact on otter or migratory fish within the River Usk Special Area of Conservation.”

Bodé is scathing of the Welsh government’s mitigation plans saying that the proposed culverts under the new road to link wildlife habitats wouldn’t work. “They’re over 100m long and only 1m wide. No water vole is ever going to go down there.” She claims that the road will fragment the already dwindling and degraded habitat.

The chosen route is one of a number of plans originally submitted. One looked at going north of the Levels, another sought to expand the existing roads south of Newport. The Welsh Government has dismissed these: “Alternative options have again been costed and appraised at the recent Public Inquiry. Independent inspectors has openly and robustly scrutinised whether the proposed Scheme is the sustainable, long term solution to the social, cultural, environmental and economic problems associated with this key gateway to Wales.”

Bode sums up the Gwent Wildlife Trust’s position: “So much valuable habitat is going to be lost forever for a new road this is going to save people a maximum of 8-10 minutes”.

The Welsh Government spokesperson was reluctant to put a figure on the actual average time saved saying “the M4 Project includes new junctions linking the strategic road network to both existing and proposed public transport links and park and ride sites. Along with cross ticketing and active travel incentivisation we can transform the way we think about mobility.” I find I'm delayed by about 3 minutes on average but I am only in the traffic jam for one junction.

The Gwent Wildlife Trust calls for more investment in public transport rather than more roads and the Future Generations Commissioner for Wales agrees, calling the road a "20th century solution to a 21st century problem". Having used the substandard train service between Newport and Bristol for six years, I feel qualified to comment.

There’s clearly room for longer trains – currently the service, run by Great Western (GWR) relies on largely old, dirty stock that comprises 2 or 3 carriages when they could easily fill four. If the service was more comfortable, more reliable, cheaper and quicker, surely more people would abandon their cars. Ideally, a shuttle service could link Bath-Bristol-Newport-Cardiff (and possibly even Swansea) creating a thriving business link between these up and coming cities.

I put this to the Welsh Government who replied that there was limited capacity to increase train numbers of the line between Bristol and Cardiff and that, essentially, decisions about rail lay in the hands of the private owner – GWR. The spokesperson instead pointed to developing “a South Wales Metro franchise” – a web of bus routes and existing train lines. It’s not easy to see how this would make a positive impact on the M4 between Newport and Bristol.

The Public Inquiry into the M4 Corridor around Newport Project closed in March this year. The Inquiry heard detailed evidence both for and against the proposals over 83 sitting days and Inspectors will submit their report to Welsh Government later this year. The Welsh Government told me “In recognition of the importance of this matter to the whole of Wales, we have committed to an Assembly debate and vote, in Government time, in before a final decision is made by the Welsh Ministers on whether to proceed to construction.

Should it go ahead, the Welsh Government would work closely with stakeholders to help ensure it is delivered to maximise the long-term benefits across the whole of Wales, for its current and future generations.”


I will be reporting on the decision on the relief road as and when it comes. For now, I am resigned to more car journeys.


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