Drivers have been warned to expect overnight delays in Berkshire as new overhead driver information signs are installed.
The southbound A34 will be closed between Beedon and the M4 interchange from 2200 BST on Wednesday until 0600 BST on Thursday.
Drivers will have to follow a diversion through Beedon and Worlds End.
The same closure is expected to be in place on Friday and drivers are advised to allow extra time for their journeys.
Meanwhile on Thursday night the northbound A34 will be closed from the junction of the A4 to the M4 interchange. Diversions will be in place.