Brynglas westbound closure scheduled overnight on 8 September

Traffic Wales scheduled maintenance on the M4 westbound through the Brynglas tunnels at Newport, in the Cardiff and Swansea direction, between junction 24 Coldra and junction 28 Tredegar Park. Its 7 to 9 September window covered two nights, each from 20:00 to 06:00. The second began on 8 September. A separate notice scheduled eastbound tunnel closures, in the Bristol direction, from 20:00 to 06:00 on the nights of 9 and 10 September. These were scheduled windows, not confirmation that either tunnel had reopened. The notices did not name a diversion route.

Nine more closures on the same hours

The following notices were listed for the night of 8 September. Nine other trunk road closures run on the same 20:00 to 06:00 hours. The M4 loses its exit slip at junction 32 Coryton and its eastbound entry slip at junction 36 Sarn, so drivers can still pass those junctions but cannot leave at Coryton or join at Sarn. The A470 northbound loses its exit slip at Nantgarw, and the A470 southbound is closed between Pentrebach and Abercynon, the third and last night of that one. The A465 is closed westbound between Neath and Llandarcy, its second and last night. The A4060 southbound is closed on two adjoining stretches around Pentrebach, filed by Traffic Wales as two separate alerts; the two stretches run as one southbound closure from Dowlais Top down to Pentrebach. The two A40 closures at Monmouth, which Cover added to its A40 report on 8 September, run 20:00 to 06:00 as well: southbound is the second of three nights, northbound the first of two. Every window and every alert number sits in the table below.

The Coryton slip

Traffic Wales labels the Coryton alert Northbound. The M4 at Coryton runs east and west only, and Traffic Wales does not say which carriageway the closing slip serves. A 2024 Welsh Government order for the junction records the eastbound and westbound carriageways as each having a dedicated exit slip on to the A470 northbound, which explains where the word Northbound comes from but not which slip closes on the night of 8 September. Traffic Wales has not resolved it.

North and mid Wales on the night of 8 September

The board runs further north as well, on slightly different hours. The A55 westbound loses a tunnel between junction 17 Conwy Morfa and junction 16A Dwygyfylchi, the second and last night of that closure, with temporary traffic lights on the stretch. A second alert holds both directions there to a 3.25 metre width limit and diverts lorries; that one runs to 10 September. Both are on 19:00 to 07:00. The A470 is closed in both directions at Ty-Gwyn east of Builth Wells on the same hours. The A487 is closed in both directions at Llanrhystud and the A458 in both directions between Buttington and the A483 interchange, both of those 19:00 to 06:00, and the A458 closure ends on the night of 8 September.

What Traffic Wales has not said

Traffic Wales publishes no diversion route for any of 8 September’s south Wales closures, so none is printed here: on these entries it gives the word Diversion, or Diversions in place, and never a route. It does not say whether the Coryton exit slip serves the eastbound or the westbound M4. And a long entry between the Hardwick roundabout at Abergavenny and Raglan, on which Traffic Wales gives no road number at all, reads bridge closed and local lanes closed and runs to 14 September, yet carries a single time, 0600, rather than a start and end time, so whether that one is nightly or round the clock is not on the page.

Traffic Wales takes calls on 0300 123 1213 and posts on X as @TrafficWalesS in south Wales, @TrafficWalesN in north and mid Wales.

Correction, 9 September 2026: an earlier version said the A55 tunnel closure between Conwy Morfa and Dwygyfylchi was on the last of three nights. Alert 594032 ran 7 to 9 September, so it was the second of two.

Correction, 9 September 2026: an earlier version said the 3.25 metre width limit on that A55 stretch bites on vans and anything towing. No road legal vehicle is that wide without a special order, and the alert diverts lorries.

Correction, 9 September 2026: an earlier version said Cover reported the two A40 closures at Monmouth on 5 September. They were added to Cover's A40 report on 8 September.

Correction, 10 September 2026: an update mixed 9 September wording into a report written for 8 September, leaving conflicting references to “tonight”. We have replaced them with dates and removed a reopening claim that rested on the scheduled end time rather than confirmation.