The A29 is set to close for two weeks near Chichester due to gasworks.
Southern Gas Networks (SGN) said Lidsey Road would be closed at Woodgate, West Sussex, from Saturday until 27 April because of essential works on pipes underneath the road.
Vehicles will not be allowed to access the road between Hook Lane and Oak Tree Road, a move which is expected to cause delays for motorists heading to and from Bognor over the Easter period.
An SGN spokesperson apologised for the disruption.
The company added: "This essential work will involve reinforcing the gas network to ensure we can maintain the increased demand for gas in the area and continue to deliver a safe and efficient gas supply.
"Our engineers will be working on the gas main in Lidsey Road between the junctions of Hook Lane and Oak Tree Lane. Due to the location of the gas pipe in the road, we'll need to temporarily close the road between these junctions."
Bus routes in the area would also be affected, SGN added.
Contractors would be working extended hours and weekends to ensure the works were completed "as quickly and as safely as possible", it added.