Traffic Signal Plan Paves the Way for HGVs to Return to M48 Severn Bridge

Heavy goods vehicles could once again cross the M48 Severn Bridge from next autumn, as National Highways prepares a traffic management solution designed to protect the ageing structure while lifting current weight restrictions.

Since May 2024, lorries over 7.5 tonnes have been diverted onto the M4 Prince of Wales Bridge after inspections revealed deterioration in the M48’s suspension cables. While the bridge has remained open to lighter vehicles, safety concerns have meant HGVs account for around 10% of daily traffic being rerouted.

To address the issue, National Highways is exploring signal-controlled systems at Junctions 1 and 2 of the M48, aimed at spacing out HGV traffic across the bridge and avoiding excess strain on its cables. Options include signal controls at on-slips or dedicated HGV lanes, designed to minimise delays while ensuring vehicles are not clustered together. The system could also be activated to hold HGVs back in the event of an incident.

Alan Feist, Programme Leader at National Highways, explained:“Safety has to come first. The bridge is still safe to use, but it was never built for today’s heavier vehicles or the volumes of traffic we see now. This restriction has been frustrating for businesses, but we’re making real progress and expect to see HGVs back on the bridge next year.”

The organisation is working with the South Wales Trunk Road Agency, Monmouthshire County Council, hauliers, and local businesses as it finalises the scheme. Implementation is scheduled for October 2026.

Opened nearly 60 years ago, the M48 Severn Bridge was not designed for the modern freight industry, where lorry weights have more than doubled over the decades. Traffic has also surged since the removal of bridge tolls in 2018, with usage climbing by 34%. Assessments in recent years have highlighted corrosion and weakening in the suspension cables, prompting the current restrictions.

Enforcement measures have already been stepped up, with Gwent Police and the Driver and Vehicle Standards Agency running Operation Wolverine. Automatic Number Plate Recognition (ANPR) cameras are now in place to ensure compliance, with Avon and Somerset Police set to move enforcement from roadside checks to primarily digital monitoring.

Emergency vehicles, coaches, buses, gritters, and recovery vehicles remain permitted to use the crossing, but other HGVs must continue to follow the official diversion via the Prince of Wales Bridge — or, if that route closes unexpectedly, via the M5 and M50.

Feist added:“We’d like to thank drivers for their patience. Restricting heavy vehicles now is vital to ensuring the M48 remains open for years to come. If we don’t act, we risk losing the bridge entirely.”