The Welsh Government has published five options to ease congestion on the M4 at Newport, ranging from widening the Brynglas Tunnels to closing junctions, as part of a new review.
On October 6, the Plaid administration announced it would order an £18m review into M4 improvements, alongside a five-year plan for short to medium-term changes. A report by Welsh Government officials details the current options, costs and impacts, and all options will be considered during the 18-month review announced by transport minister Mark Hooper.
Five proposals examined
The report assesses the advantages, disadvantages, costs and timescale of five proposals:
- Widening of the Brynglas Tunnels
- Works to the A48 Southern Distributor Road and A4810 Steelworks Access Road (Queen’s Way) corridor
- A targeted package of A48 Southern Distributor Road improvements
- Closures of M4 junctions, either fully or at specific times, including a proposed full closure of junction 27 and closure of east-facing slips at junctions 25 and 26
- Traffic management measures and improved HGV rest facilities to encourage lorry drivers to use the A465
The report also includes public transport options, such as additional rail services on the South Wales Mainline, improvements at Severn Tunnel Junction, new rail stations on the mainline, and a new Newport-Cardiff Bus Rapid Transit service. It did not consider a new motorway or a new Magor-Castleton tunnel due to the "affordability, environmental and planning challenges they would likely face". Tolls were outside the scope of this review, but all options are understood to be on the table for at least the initial phase of the 18-month plan.
Costs and impacts of each option
Widening the Brynglas Tunnels would cost £1.7bn and take 12 years, improving capacity and allowing traffic to move freely at a pinch point, but it carries "high engineering/geotechnical risk". The scheme would use the existing hard shoulder to create a dual four-lane motorway between Junction 29 (Castleton) and Junction 26 (Malpas), keep the 50mph speed restriction, and construct a new westbound three-lane tunnel at Brynglas. It would cause "major construction disruption, property acquisition and potential impacts on habitats and species".
Works to the A48 and A4810 would cost £1.8bn and reduce M4 traffic by 6%, making both roads dual carriageways and requiring changes to junctions. This needs agreement from Newport council and could impact the Gwent Levels. A targeted A48 improvements package would cost £1.7bn, take eight years, and deliver a 5% reduction in M4 traffic with "significantly less disruption". It would involve changes to Maesglas Road, Usk Way, Corporation Road, Nash Road, Queensway Meadows, Hartridge and Beatty Road, with local widening and signals at key junctions.
Junction closures and alternative routes
A full closure of junction 27 and closure of east-facing slips at junctions 25 and 26 would cost £14m, take two years, and result in a 3% reduction of traffic around Newport on the M4. The report says this would reduce use of the M4 by local traffic, particularly through the Brynglas Tunnels, but would displace traffic and increase pressure on remaining junctions and local roads around Malpas, High Cross and Ridgeway. Encouraging use of the A465 with variable message signs and HGV rest facilities would cost £49m, take three years, and result in a 1% reduction in traffic.
The report says the fastest and cheapest scheme is changing the existing M4, including junction closures and promoting the A465. This would cost £63m, take less than three years, and reduce traffic by 4%. Combining this with public transport options would cost £1.2bn, take six years, and result in an 11% reduction in traffic. Widening the Brynglas Tunnels alongside M4 changes would cost £1.7bn, take 3% of traffic off the route, and combined with public transport plans, reduce traffic by up to 10% at a cost of £2.9bn over 12 years.
The A48 and A4810 capacity increases, combined with junction closures, would offer a more attractive alternative corridor south of Newport while the A465 provides a resilient route north. This option would not require closing the M4, but sections of the A48 would need to close for up to four years during construction, causing major impacts on the local road network.
