National Highways identifies solution to M48 HGV weight restriction

National Highways’ preferred solution that will ensure there are never too many HGVs using the Severn crossing, enabling the current weight restriction to be removed, has been identified.

GVs weighing over 7.5 tonnes are currently diverted onto the M4 Prince of Wales bridge.

To solve this, from next autumn HGVs will leave the M48 at Junctions 1 (westbound) and Junction 2 (eastbound) via the off-slip roads with re-entry controlled by signals on the on-slips.

Following engagement with local authorities and businesses on proposals, this is a preferred solution for the medium-term, while longer term options are explored by National Highways.

For the vast majority of the time the system would operate ‘freely’ to release HGVs so they are spread out across the length of the bridge and not concentrated together, creating very little delay to HGV or car traffic. 

The system can also be used to keep HGVs off the bridge if there is a significant incident in the area.

Alan Feist, Programme Leader for National Highways, said: “Safety is our number one priority, and this weight restriction is about keeping the bridge safe for use now and for years to come.

“Whilst the bridge remains safe, it was not designed and built for today’s levels or weight of traffic. Vehicles have got heavier, and traffic levels have increased significantly over the last 60 years, putting greater load on the cables.

“We appreciate that this has been disruptive for businesses and hauliers, but we have been working at pace to reach this solution and are pleased to be on track to get HGVs back onto the M48 Severn Bridge next year.”

Roads and Buses Minister, Simon Lightwood, said: “I am pleased to see National Highways making progress to allow HGVs to return to the M48 Severn Bridge next year.

“Safety remains the number one priority, while ensuring this important crossing continues to serve the businesses and communities who depend on it.”

Cabinet Secretary for Transport and North Wales, Ken Skates, said: “We welcome and support the news from National Highways. We will continue to engage with the team as measures to address a longer-term solution for the Severn Bridge weight limit are explored.”  

Following safety inspections, since May this year only vehicles below 7.5-tonnes in weight have been able to use the M48 Severn Bridge due to deterioration of the supporting cables.

To minimise further damage, heavier vehicles travelling between England and Wales have been diverted via the Prince of Wales bridge, with the M48 bridge remaining open to all other traffic.

The M48 Severn Bridge carried roughly 32,000 vehicles a day in 2024, 3,270 of which were over 7.5t, meaning around 10 per cent of traffic is currently diverted via the M4 Prince of Wales Bridge with the current restrictions in place.

Since the bridge opened nearly 60 years ago, the size and weight of HGVs has increased significantly due to evolving transport demands, some rising from 22 tonnes to 44 tonnes.

Traffic numbers have also increased over the decades. Since the tolls were removed on the bridge in 2018 there has been a 34% increase in traffic and these changes mean a substantial increase in weight over the bridge, which it was not designed for.

The M48 Severn Bridge has undergone several major assessments and interventions related to its main suspension cables due to concerns about corrosion and strength reduction, caused by its exposure to harsh weather conditions.

In 2022/23, an assessment of the bridge’s main cables was carried out followed by further laboratory testing. Finalised in December 2024, the results revealed that the main cables are deteriorating and not as strong. Due to these results, it was recommended that National Highways reduce the load on the bridge to minimise further damage.

Alan added: “We’d like to thank drivers for their support and must stress that only vehicles up to 7.5 tonnes in weight should use the bridge.

“Continued use of the bridge by heavier vehicles could ultimately see it closed to all traffic. We are acting now to prevent this from happening.”

The M48 Severn Bridge remains open to all emergency vehicles, scheduled buses, coaches, gritters and recovery vehicles.

If there is an unplanned closure of the Prince of Wales bridge, vehicles over 7.5t need to follow the official diversion route via the M5 and the M50.