Works taking up to six weeks are starting on Richmond Hill from today.
The Department of Infrastructure says its to repair parts of and resurface the road, as one section has become sunken.
It will involve the road from the base of Richmond Hill up to the Spring Valley roundabout.
For the bulk of the period all traffic will be diverted onto the road between Kewaigue Hill and the base of Richmond Hill, with that road having a temporary 30mph speed limit.
This diversion route will open at 9:30am today once commuter traffic has eased.