Traffic light system to allow HGV Severn Bridge return

Heavy goods vehicles (HGVs) will have to wait at a set of traffic lights to use the Severn Bridge when it re-opens to vehicles weighing more than 7.5 tonnes next year.  

National Highways has published details on its preferred solution for allowing HGVs to start using the crossing again after they were banned in May. 

Engineers had discovered deterioration to the supporting cables during safety inspections, forcing HGVs to instead use the M4 Prince of Wales bridge to travel between England and Wales.

In September, National Highways said it was considering two options at junctions one and two of the M48 to manage loads that would allow HGVs back across the bridge without overloading its cables.

From next autumn, it has decided that HGVs will leave the M48 at junctions one (westbound) and junction two (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, National Highways says this is the preferred solution for the medium-term, while it explores a longer-term solution.

For the vast majority of the time, the system will operate ‘freely’ to release HGVs so they are spread out across the length of the bridge and not concentrated together.

National Highways insists that this will create “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.”

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

Roads and buses minister, Simon Lightwood, welcomed the plans 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,” he added.

Since the bridge opened almost 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.

Feist said: “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 weighing more than 7.5 tonnes need to follow the official diversion route via the M5 and the M50.