**Severn Bridge Heavy Vehicle Ban Expected to Cause Significant Disruption on M4 Corridor**
Motorists making their way between Wales and England are being warned to anticipate heightened congestion along the M4, following a decision to introduce a weight restriction on the M48 Severn Bridge. As of Tuesday, 27 May 2025, vehicles exceeding 7.5 tonnes will no longer be permitted to cross the historic structure, a safety measure expected to remain in place for a minimum of 12 months.
The restriction arises in response to worrying findings about the condition of the bridge. National Highways, the government agency responsible for major roads, revealed that recent inspections showed the bridge’s crucial support cables were showing signs of deterioration. In a bid to extend the lifespan of the 60-year-old bridge and ensure the safety of all road users, authorities made the decision to limit the weight of vehicles traversing the span.
Consequently, all affected heavy goods vehicles (HGVs) will be rerouted to the M4’s Prince of Wales Bridge, causing concern amongst experts about the potential repercussions for traffic flow. According to figures from last year, around 32,000 vehicles use the M48 Severn Bridge daily, with heavy vehicles forming roughly a tenth of that total. With those 3,270 daily HGVs shifting over to the M4, traffic volumes on this already-busy route are expected to increase sharply.
Rhydian Jones, who serves as a car insurance specialist at Confused.com, explained, “Directing thousands of HGVs onto the M4 is likely to create serious congestion, particularly during already busy periods.” He advised motorists to allocate extra time to their journeys, avoid peak travel hours where possible, and keep abreast of traffic updates. “With key destinations like Bristol and Heathrow airports along the affected route, even minor delays could result in missed flights and significant inconvenience,” Jones cautioned.
The backdrop to these changes is a marked increase in both the weight and number of vehicles using the M48 Severn Bridge. Since the removal of toll charges in 2018, National Highways reports a 34% surge in traffic. This, coupled with increasingly heavy lorries, has put a level of strain on the structure for which it was never designed. The assessment carried out late last year highlighted the weakening of the bridge’s main cables—prompting officials to act swiftly to avert more severe restrictions or even full closure in the future.
Chris Pope, Programme Delivery Manager for National Highways, sought to reassure the public, stating, “Our priority is, and always will be, the safety of bridge users. The new restrictions are designed to preserve the M48 for future generations, whilst still keeping it open for the majority of traffic.” He made clear that only vehicles under the new weight threshold would be allowed to cross, and stressed the importance of compliance to avoid more drastic steps down the line.
Despite the changes, certain essential vehicles will remain exempt from the ban. This includes emergency service vehicles, buses, coaches, gritting lorries, and recovery vehicles, all of which will still be allowed to use the M48 crossing under the new regime.
Should an unexpected closure of the M4 Prince of Wales Bridge occur while the restrictions are in force, an official diversion route will be in operation via the M5 and M50—potentially adding further mileage and time to haulage journeys. To help enforce the new rules, National Highways is also considering the installation of Automatic Number Plate Recognition (ANPR) cameras, which would help identify and deter unauthorised crossings by overweight vehicles.
As communities and commuters adjust to these changes, local and national authorities continue to monitor the situation closely. Both the short- and longer-term implications for cross-border transport, regional economies, and everyday road users remain under scrutiny, as the region adapts to the new realities of a key artery under strain. Drivers are being urged, above all, to stay informed and plan ahead for the coming months of disruption, while infrastructure improvements and safety checks are carried out.
For ongoing updates on travel and infrastructure developments in Wales and the southwest of England, drivers are advised to consult official National Highways channels and regional travel bulletins.