National Highways signals solution to M48 HGV weight restriction
Signals to ensure there are never too many HGVs using the M48 Severn crossing form part of a solution that will allow the current weight restriction to be removed next Autumn.
This would mean HGVs weighing over 7.5 tonnes are no longer diverted onto the M4 Prince of Wales bridge.
National Highways is to engage with local authorities and hauliers on proposals.
Following safety inspections, since May this year only vehicles below 7.5-tonnes in weight have been able to use the M48 Severn crossing after inspections showed deterioration to 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.
National Highways is looking at two options at both Junctions 1 & 2 of the M48, to manage loads which would allow HGVs back across the bridge without overloading its cables.
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 on these options and are pleased to be in on track to get HGVs back onto the M48 bridge next year.”
In planning a solution, at Junction 1, National Highways proposes to route westbound HGVs off the M48 via the off-slip and on-slip and control re-entry by way of signals.
One option would control access for all vehicles whilst another would have a dedicated HGV lane, controlling access back onto the bridge.
At Junction 2, the proposal is to either control HGV movements using traffic signals across the roundabout or, like at Junction 1, control HGV access from the eastbound on-slip using signals.
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 in close proximity, 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.
National Highways is now engaging with South Wales Trunk Road Agency, local highways authorities, including Monmouthshire County Council, and several businesses and hauliers in the area, ahead of implementation by October 2026.
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 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.
On enforcement, Operation Wolverine with Gwent Police has been running for three months, and ANPR cameras have also now been installed at either end of the structure.
National Highways continues to work at pace with Avon and Somerset Police as it transitions from physical enforcement to predominately digital via ANPR cameras.
For more information, please visit the Severn Bridge website.
Notes to Editors
National Highways is the wholly government-owned company responsible for modernising, maintaining and operating England’s motorways and major A roads.
Real-time traffic information for England’s motorways and major A roads is available via the Traffic England website, local and national radio travel bulletins, electronic road signs and mobile apps. Local Twitter services are also available.
For further information please contact National Highways' press office (24hrs) on 0844 693 1448 and select the most appropriate option:
Option 1: National enquiries (9am to 5.30pm) and out of hours for urgent enquiriesOption 2: North West (9am to 5.30pm)Option 3: Yorkshire and North East (9am to 5.30pm)Option 4: West Midlands (9am to 5.30pm)Option 5: East Midlands (9am to 5.30pm)Option 6: East (9am to 5.30pm)Option 7: South East (9am to 5.30pm)Option 8: South West (9am to 5.30pm)
