What’s happening with the M48 Severn Bridge? Why is it closed so often? How does it affect your commute, and what alternative routes are available? With increasing maintenance, adverse weather conditions, and newly introduced vehicle restrictions, the M48 bridge closure has become a significant issue for road users travelling between England and Wales.
This blog offers a comprehensive breakdown of the reasons behind the closures, the differences between the M48 and M4 bridges, the impact on commuters and businesses, and how to stay informed about travel disruptions.
Why Is the M48 Severn Bridge Closed More Often Than Before?
The M48 Severn Bridge, a key connection between South Gloucestershire and Monmouthshire, has experienced a notable rise in closures in recent years. The increasing frequency of these closures is not without reason.
As a structure completed in the 1960s, the bridge is ageing and requires more maintenance to remain safe and operational. Routine inspections, structural improvements, and urgent repair works are essential due to its design and the load it continues to carry.
Unlike modern motorways, the road surface on the M48 is narrower, which means there is limited space for maintenance teams to work safely while keeping lanes open. As a result, full or partial closures are often necessary.
The closure pattern has also been influenced by changing operational policies. Previously, during high winds, traffic officers physically filtered high-sided vehicles such as lorries and motorcycles from crossing. This method, although it reduced the number of full closures, proved unsafe for traffic officers, especially during poor weather.
In 2022, National Highways formally ended the filtering practice, opting instead for complete closures when wind thresholds are exceeded, prioritising safety over convenience.
What New Restrictions Are in Place on the M48 Bridge?
A significant change took effect on 27 May 2025, when a new weight restriction was imposed on the M48 Severn Bridge. Vehicles exceeding 7.5 tonnes are no longer permitted to cross. This measure was introduced after engineers determined that the main suspension cables of the bridge had deteriorated to the point where reducing the load was essential to maintain safety and prolong the bridge’s usability.
This restriction impacts heavy goods vehicles (HGVs), some large coaches, and freight transport, which must now use the M4 Prince of Wales Bridge as an alternative route.
The decision to implement the restriction followed a detailed engineering assessment. By reducing the strain on the suspension system, authorities aim to delay the need for more extensive repairs or reconstruction.
Importantly, this change allows the bridge to remain accessible to cars, vans, and light commercial vehicles, ensuring continued regional connectivity.
What Makes Wind a Serious Risk for the M48 Severn Bridge?
The geographical position of the Severn Estuary makes both bridges vulnerable to strong winds. However, the M48 Severn Bridge lacks modern wind defences, such as high barriers that are installed on the M4 Prince of Wales Bridge. As a result, the older bridge is significantly more prone to weather-related closures.
Wind management on the M48 has evolved in recent years. Rather than relying on local weather reports or regional forecasts, dedicated wind monitoring equipment installed directly on the bridge informs closure decisions. These devices provide real-time data that is more accurate than general weather apps or measurements from nearby towns.
The wind-related closure policy currently follows a structured threshold model:
| Wind Speed (Knots) | Action Taken |
| 30 knots | Advisory 40mph speed limit |
| 35 knots | Closure of leeward lanes using Red X signs |
| 40 knots | Full closure of the M48 Severn Bridge |
| 70 knots | Both M48 and M4 bridges closed |
These thresholds are non-negotiable and based on safety risk assessments. While members of the public may not feel strong winds on the ground, conditions on the bridge deck—elevated above sea level—can be far more severe.
Why Was the Lighting Switched Off on the M4 Prince of Wales Bridge?
Although the M4 Prince of Wales Bridge is fully operational and open in both directions, a temporary lighting issue is affecting the structure. Following emergency maintenance, authorities have had to switch off the bridge lighting system.
The absence of lighting raises safety concerns, especially during night-time travel. To address this, a 40mph advisory speed limit has been introduced for the hours of darkness. Drivers are urged to reduce their speed and increase their awareness while crossing the bridge at night until lighting systems are restored.
Despite the lighting issue, the bridge remains structurally sound and is the primary diversion route when the M48 is closed.
What Maintenance Work Is Being Carried Out on the Severn Crossings?
Maintenance is an ongoing requirement for both the M48 and M4 bridges, but especially so for the M48 due to its age and design. National Highways continues to perform a wide range of tasks to keep the bridge serviceable and safe for all users.
Some of the maintenance operations include:
- Suspension cable inspections and tension adjustments
- Surface resurfacing, particularly after winter months
- Installation and upgrade of safety barriers
- Lighting repairs and system enhancements
- Structural assessments below the deck and at expansion joints
One important factor to understand is that not all work is visible to drivers. Much of the work occurs beneath the road surface, on cables, or requires long curing times for materials used. This means that, even when no activity is apparent, closures may still be required while materials set or while waiting for the next phase of repair.
Given the narrow width of the M48, safe working areas are limited, which further necessitates full closures more often than on modern roadways.
How Does the M48 Bridge Closure Affect Commuters and Freight?
The closure of the M48 has widespread implications, not just for daily commuters but also for regional logistics and local economies. Regular users of the M48 often face extended journey times, especially when diverted to the M4 during closures.
For heavy goods vehicle operators, the introduction of the weight restriction means a permanent change to routing logistics. This may result in:
- Longer travel distances
- Higher fuel consumption
- Increased costs due to rerouting
Local businesses in towns such as Chepstow, Caldicot, and Aust may also experience a drop in passing trade during full closures. Emergency services must adjust their response plans, and public transport providers must communicate reroutes or delays more frequently.
Despite the inconvenience, National Highways has made it clear that the priority remains public safety and bridge longevity.
What Are the Best Alternative Routes During M48 Closures?
The most common diversion when the M48 is closed is via the M4 Prince of Wales Bridge, which provides a direct route between South Wales and South West England. This bridge, opened in 1996, was designed to handle higher volumes of traffic, including heavy goods vehicles.
In the rare event that both bridges are closed—usually due to severe storms—drivers can follow this longer route:
M5 → M50 → A40 → A449
This route, while significantly longer, ensures connectivity between regions during major events.
For non-drivers, train services continue to offer an alternative. Routes between Bristol, Newport, and Cardiff are reliable and unaffected by bridge closures. Bus services may also be rerouted accordingly, although delays are possible.
Footpaths and cycleways on the M48 typically remain open, except during extreme weather or serious incidents.
What Is the Current Status of the Bridges This Week?
For the week of 26 December 2025 to 1 January 2026, there are no scheduled closures for either the M48 or M4 bridges.
However, road users are encouraged to monitor daily updates, especially during the winter months, when emergency closures due to wind or ice are more common.
How Do the M48 and M4 Bridges Compare Today?
| Feature | M48 Severn Bridge | M4 Prince of Wales Bridge |
| Year Opened | 1966 | 1996 |
| Structural Age | Older | Modern |
| Wind Defences | None | Present (barriers) |
| Lighting | Operational | Temporarily off |
| HGV Access | Prohibited (>7.5t) | Allowed |
| Width of Road | Narrow | Wider |
| Closure Frequency | Higher | Lower |
| Main Function | Local/Regional traffic | National and commercial traffic |
Frequently Asked Questions
Why is the M48 bridge experiencing more closures now than in the past?
Ageing infrastructure, safety regulations, and changes in wind management have increased closure frequency.
Can HGVs still use the M48 bridge?
No. As of May 2025, vehicles over 7.5 tonnes are prohibited due to load restrictions on the main suspension cables.
Is the M4 Prince of Wales Bridge affected by the same issues?
Not to the same extent. While it is occasionally closed in extreme weather, it is newer, wider, and equipped with better wind protection.
Are closures planned in advance or reactive?
Closures can be both. Planned maintenance is scheduled and communicated, but weather-related closures may happen at short notice.
Where can I get the most accurate updates?
The official @2SevernBridges account on X (Twitter), National Highways website, and Traffic Wales provide up-to-date alerts.
Are pedestrian and cycling paths also closed during wind events?
Usually not. These paths remain open unless there’s a severe storm or emergency incident requiring full closure.
Is there any plan to replace the M48 bridge in the near future?
Currently, no replacement is planned. Maintenance and restrictions are intended to preserve the bridge’s long-term viability.
