One lane over the hill will be closed from 9pm tomorrow night, Yuttana Phithak, chief of the Phuket Highways office, explained in an announcement issued late today (June 24).
Traffic over the hill will be reduced to one lane through to 5am Sunday morning (June 26), Mr Yuttana said.
The area to be affected is the steep section of road on the Kathu side near the Patong City sign, he added.
Mr Yuttana did not specify which lane would be closed, or whether each lane would be closed in turn as the work is carried out.
However, Mr Yuttana apologised for the inconvenience.
People with queries were asked to call the Department of Highways hotline 1586.