Motorists travelling between Torfaen and Monmouthshire face significant disruption from late January as the Welsh Government prepares to implement a sweeping series of temporary closures, speed limits and traffic restrictions along the A4042 trunk road.

Welsh Ministers have announced their intention to introduce the measures under section 14 of the Road Traffic Regulation Act 1984, with the legal order expected to be made from this week. The works, described as essential maintenance on or near the route, will take place between Mamhilad Roundabout in Pontypool and Hardwick Interchange on the outskirts of Abergavenny.

The restrictions will begin at 7pm on January 26 and may operate on an intermittent basis for up to 18 months. Officials say access for local traffic will be maintained up to the points of closure, with diversions clearly signposted.

Under the proposed order, all vehicles—except those used by emergency services or directly involved in the works—will be prohibited from travelling on the affected stretch of the A4042 for the duration of the closures. A full ban on overtaking will also be introduced along the same section of road.

In addition, temporary speed limits of 40mph and, in some areas, limits of just 10mph will be imposed at various points between the two roundabouts. These reduced limits will apply in multiple zones, including near Croes‑y‑Pant Lane, Park y Brain Lane, Old Abergavenny Road, Llwyn Celyn Lane and the B4269 at Gypsy Lane—reflecting the extent and complexity of the planned works.

The diversion routes for motorists during closure periods are lengthy and are expected to add considerable journey time. Drivers heading northbound from Mamhilad will be redirected southwards along the A4042 to Grove Park Roundabout, then on to Newport’s Southern Distributor Road via Old Town Dock Junction, before heading north on the A449 from the Coldra Interchange and finally west along the A40 to reach Hardwick Interchange. Southbound travellers will follow the same diversion in reverse.

Motorway users face an additional detour: northbound traffic will join the M4 eastbound at Grove Park Roundabout, exiting at Junction 24 (Coldra) to join the remainder of the primary diversion route.

Local authorities will manage traffic on side roads affected by the closures, with arrangements tailored to each council’s requirements and all restrictions will be fully signposted once in force.