The M4 through Newport is an important road connection between southern Wales and southern England. For several years, it’s been plagued by congestion problems. It’s been argued that these traffic problems have harmed the south Wales economy.

Proposals for a full M4 bypass date back to the early 1990s and before devolution. The only serious developed proposals for a bypass (called the “Black Route”) emerged during the 2010s. The Welsh Government spent up to £120 million developing plans and making compulsory purchase orders for land¹.

In June 2019, the Welsh Government abandoned plans for a bypass. This was due to the growing costs of the project (estimated at the time to be around £1.6 billion) and the route’s impact on the environmentally sensitive Gwent Levels.

Plaid Cymru and high-profile transport experts, such as Prof. Stuart Cole, supported an alternative “Blue Route”, which would’ve seen upgrades to the existing A48 and A4810. These plans were never taken forward seriously.

A new assessment of the potential long-term options was published in October 2026. As a short-term option, the Welsh Government is actively considering selective junction closures on the M4.

On 21st October 2026, the Senedd voted in a non-binding motion to support work resuming on a Newport bypass and opposing proposed junction closures.

The M4 around Newport was constructed during the 1960s and now falls far short of modern motorway standards, with tight corners and short slip roads.

The Brynglas tunnels are a notorious “pinch point”, forcing the M4 to narrow to 2 lanes in each direction. As the M4 is the most convenient or direct way to cross Newport, local traffic often mixes with longer-distance traffic, making congestion worse.

In the years following the bypass’s cancellation, the Welsh Government changed its transport policy to presume against new road projects².

As an alternative to a bypass, a commission led by Lord Burns (“Burns Commission”) put forward proposals for public transport improvements in and around Newport. These plans include at least five new railway stations between Cardiff Central and Severn Tunnel Junction, as well as bus priority measures and improvements to walking and cycling facilities³.

Estimated (and manually counted) measures of the amount of traffic using the M4 through Newport are available below (from the UK Department of Transport).