Motorists are advised of night work will begin on a section of the Hume Highway at Mittagong from September 1.
This will involve work on the Gibbergunyah twin bridges.
A Transport for NSW spokesperson said this essential maintenance would require night time lane closures in each direction on the Hume Highway.
"Recent inspections have indicated work is needed to replace the bridge screws and finger plates to help strengthen the bridge and help reduce ongoing maintenance costs," the spokesperson said.
The work will take place over six weeks, weather permitting, and work hours will be between 8pm and 5am Sunday to Thursday.
During work hours, two of three southbound lanes will be closed for three weeks from September 1 and two of three northbound lanes will be closed for three weeks from September 22.
Electronic message boards will be in place to notify motorists of the changed traffic conditions.
Motorists are advised to drive to the conditions, and follow the directions of signs and traffic control.
Transport for NSW thanks the community for its patience while work is carried out.
For the latest traffic updates call 132 701, visit livetraffic.com or download the Live Traffic NSW App.