MOSS Vale Road from the top of Cambewarra Mountain and down its Kangaroo Valley side will be closed to most traffic between 9am and 3pm until Friday, May 9.
Roads and Maritime Services will be carrying out essential maintenance on the section, including resurfacing and replacing the existing guard rail.
School buses and tourist coaches will be allowed to pass through under traffic control, but other traffic will be detoured via the Illawarra Highway, Princes Highway and Sheepwash Road, adding about one hour, 20 minutes to travel times.
If wet weather interferes with the work, it will be carried out on the next available day.
Roads and Maritime Services has asked motorists to use caution when travelling through the work site.