A mountain road in Rhondda Cynon Taff will be closed for a week to allow resurfacing and rock netting work to take place.
The A4061 Bwlch-y-Clawdd Road will be shut from Treorchy to north of the village of Nantymoel in Bridgend county, just after the A4107 junction.
It will be closed from Tuesday for one week after a £20m Rhondda Cynon Taf council investment in roads in 2017-18.
Leader Andrew Morgan said work is "future-proofing" routes.
The Easter school holidays were chosen to minimise disruption for commuters, he added.