The M48 Severn Bridge has an important Saturday evening changeover on 8 August 2026. National Highways says both carriageways remain closed until 20:00, with traffic diverted by the M4 Prince of Wales Bridge. From 20:00, a longer-term contraflow is due to begin, using one narrow lane in each direction on the eastbound carriageway.
If you are travelling between South Wales and South West England this evening, the useful question is not simply “Is the bridge open?” It is “Which arrangement is operating when I arrive?” Check the National Highways Severn bridges update and live traffic information shortly before leaving, because planned traffic management can change.
Before 20:00: plan for the full diversion
Until the scheduled changeover time, the M48 crossing is listed as closed in both directions. The official diversion runs by the M4 Prince of Wales Bridge. Do not follow a navigation shortcut onto small local roads simply because the calculated distance looks shorter. Use the signed route, allow extra time and keep enough fuel or battery range for slower traffic.
If your destination is Chepstow, National Highways says access will be maintained, but follow the signs in place rather than assuming your usual junction approach is available. Decide on a safe stopping point before the diversion if you need to check the route or contact someone. Never stop on a slip road or hard shoulder to adjust navigation.
After 20:00: expect a narrow 30mph contraflow
From 20:00, the planned arrangement is a single narrow lane in each direction on the eastbound carriageway while work continues on the westbound side. National Highways lists the lane width as three metres, with a 30mph limit and average-speed cameras. The contraflow is scheduled to remain until 20:00 on Friday 18 September.
A narrow lane needs calm, predictable driving. Join the correct lane early, keep a steady position and avoid touching the cones or temporary barrier with a late correction. Leave a generous gap to the vehicle ahead so you can brake progressively. The speed limit is a ceiling, not a target; reduce speed further if traffic, visibility or instructions require it.
Large mirrors, roof boxes and wide loads deserve extra thought before departure. Confirm that everything is secure and that your vehicle is suitable for the signed lane. If you are towing, driving a wide vehicle or carrying an unusual load, check current official restrictions before starting rather than making the decision at the bridge.
Prepare the car while it is safely parked
Dusk can combine low sun, reflections from the estuary and changing work lights. Clean the windscreen inside and out, top up washer fluid and check that every exterior light works. Keep sunglasses available for the earlier part of the journey, but remove them as light fades. Set navigation and music before moving.
Secure bags, bottles and charging cables so they cannot move under braking. Put a high-visibility vest where it can be reached without unloading the boot. Keep an escape tool with a seatbelt cutter firmly secured inside the passenger compartment and reachable by an adult, not loose in a door pocket or buried under luggage.
A warning triangle should never be placed on a motorway. On other roads, use one only when it is legal and genuinely safe. If your vehicle develops a problem on a motorway, prioritise reaching a place of relative safety and follow National Highways guidance. Do not attempt a roadside repair beside live traffic.
JUFO recommendation: 3-in-1 Roadside Breakdown Kit — £17.95
The JUFO 3-in-1 Roadside Breakdown Kit groups practical visibility and emergency items in one compact set for everyday UK driving. Keep it secured in a consistent place and check the contents before a longer journey. It supports preparation; it does not replace breakdown cover, official instructions or safe judgement.
A simple Saturday evening sequence
Check the live bridge status while parked. If you expect to arrive before 20:00, follow the signed M4 diversion and allow a realistic buffer. If you expect to arrive after 20:00, prepare for one narrow lane each way, a 30mph limit and average-speed enforcement. If the changeover is delayed, trust the signs and traffic officers rather than an earlier screenshot.
This evening’s transition is easier when the plan is made before the engine starts. A live route check, clean glass, steady spacing and securely stored equipment can turn a complicated-looking changeover into a controlled journey.
