Overnight closures hit both Severn crossings for maintenance
Eastbound M48 and westbound M4 shut from 8pm to 6am on Sep 28‑29, drivers redirected via alternative routes.
Both Severn crossings will be partially closed overnight on Monday 28 September as structural maintenance work begins on the M48 Severn Bridge and the M4 Prince of Wales Bridge.
The eastbound carriageway of the M48 is set to close between junctions 2 and 1 at 20:00, remaining shut until 06:00 the following morning.
Drivers heading east into Wales will be forced to use the westbound M4 Prince of Wales Bridge and follow the prescribed diversion.
Meanwhile the westbound carriageway of the M4 between junctions 21 and 23 will close at 21:00, also reopening at 06:00 on Tuesday.
Westbound traffic will be redirected onto the eastbound M48, crossing the Severn Bridge in the opposite direction.
Highways officials have warned that the combined closures could add up to 30 minutes to journeys for commuters and freight operators.
“The Severn crossings are vital links for both local traffic and long‑distance journeys,” a spokesperson for the Welsh Government said, adding that the works are essential to maintain the safety of the structures.
The M48 diversion will see drivers travel north on the M4 to junction 20, exit onto the M5, then re‑join the westbound M4 before crossing the Severn via the M48.
Motorists are advised to allow extra travel time and to check live traffic updates before setting off.
Freight firms have already begun to adjust delivery schedules, with some opting to postpone loads until after the early‑morning reopening.
Local authorities in Monmouthshire and Gloucestershire have issued alerts to residents, urging them to avoid non‑essential trips during the closure window.
Public transport operators are also adapting services; several bus routes that normally use the Prince of Wales Bridge will run via the M48 for the duration of the works.
Rail passengers are unlikely to be directly affected, but the road closures may increase demand for train services across the Severn Valley line.
Road safety teams will be on site throughout the night to manage traffic flow and respond to any incidents.
Temporary signage and lane markings have been installed on both bridges to guide drivers onto the correct diversion routes.
Emergency services have been briefed on the closures and will maintain response times via alternative routes.
Construction crews will carry out structural inspections, corrosion treatment and repainting of key steel components on both bridges.
The maintenance programme is part of a wider £150 million investment plan aimed at extending the lifespan of the Severn crossings.
Previous full closures of the Prince of Wales Bridge in 2022 and 2023 caused significant disruption, prompting authorities to adopt a staggered approach this time.
Transport for Wales has reminded drivers that the Severn crossings handle over 30 million vehicle movements each year, underscoring the importance of keeping at least one direction open.
Local businesses in Chepstow and Newport have expressed concerns about potential loss of customers during the closure period.
“We will do everything we can to minimise the impact on shoppers and commuters,” the spokesperson added.
Traffic monitoring will continue after the bridges reopen to assess any residual congestion.
Drivers who miss the diversion signs are urged to pull over safely and follow the on‑screen navigation prompts.
Overall, officials stress that the overnight works are designed to limit disruption while ensuring the long‑term safety of two of Wales’s most critical transport arteries.
Motorists are encouraged to plan ahead, use real‑time traffic apps and consider alternative travel modes where possible.