As of Monday February 28, a temporary one-way system will come into use on the A472 between the Royal Oak and Cwm Du roundabouts in Ystrad Mynach.
BAM Nuttall and Dwr Cymru Welsh Water will be carrying out the roadworks in preparation for the opening of Ysbyty Ystrad Fawr.
The temporary one-way system is likely to be in place for up to two weeks.
Residents are advised that A472 eastbound movements will continue as normal from the Royal Oak roundabout towards the Cwm Du roundabout.
For A472 westbound traffic, a diversion will be signposted, which will require use of the Dyffryn Industrial Estate roundabout, to the Coopers Arms Pub traffic signals, and along Caerphilly Road to rejoin the A472 at the Royal Oak roundabout.