The closure will affect both the eastbound and westbound carriageways between Porthyrhyd Junction and Cross Hands Junction, as well as the section from 175 metres west of the Nantycaws exit to the Pen-sarn Roundabout. The full notice can be found on the Public Notice Portal https://publicnoticeportal.uk/notice/traffic-and-roads/68c93fc3530d4800568a0110The alternative route for eastbound traffic between Porthyrhyd Junction and Crosshands Junction is via the B4310, Heol Blaenhirwaun, Carmarthen Road and the A476. Vice versa for westbound traffic. For westbound traffic between Nantycaws and Pen-sarn Roundabout from the A48 Nantycaws exit is via Heol Llangynnwr, continue until Llangunnor Roundabout, first exit onto the A40 and continue until Pen-sarn Roundabout. Vice versa for eastbound traffic.