A4042 set to be closed overnight for essential work to take place The Welsh Government is to ban all traffic on the A4042 between Caerleon Roundabout and Cwmbran Roundabout so that work on or near the trunk road can be carried out. The temporary prohibition will come into for on March 7, 2021 and will operate overnight from 8pm to 6am on an intermittent basis for not longer than 18 months. The temporary prohibition of vehicles: 1. The length of the A4042 westbound carriageway which extends from its junction with the western side of the Caerleon Roundabout to the nosing of the M4 Junction 25A westbound exit slip road.