One lane of a dual carriageway along the A24 at Ashington will be closed for two weeks from Sunday, November 11.
The inside lane of the southbound section of carriageway is being shut so urgent parapet and fencing work can be done at Hole Street in Ashington.
It will affect about 500 metres of the southbound Ashington bypass.
West Sussex County Council said the £75,000 scheme, being carried out by its contractors Balfour Beatty, is necessary to ensure the carriageway remains safe for the public to use.
The closure will be in place 24 hours a day until the lane is re-opened.