Richmond Hill is closed today and tomorrow.
A forty-four-week scheme to improve safety there gets fully under way on Monday.
However the road will be closed to traffic this weekend for preparatory work.
It's shut from Spring Valley roundabout to Mount Murray Back Road, apart from for residents and emergency vehicles.
Richmond Hill will re-open at midnight on Sunday with traffic restricted to one lane in each direction and a 30 mph speed limit will also be in place from Spring Valley roundabout to the top of Richmond Hill.
Project Engineer Matt Asthill explains what they will be doing for the next two days: