Motorists are advised of changed traffic conditions on the Mitchell Highway about 14 kilometres north of Nyngan for culvert replacement and shoulder widening work.
Work has started along a 10-kilometre section of highway and will take about six months to complete, weather permitting.
Crews will be working between 7am and 6pm from Monday to Saturday.
Changed traffic conditions including single lane contra-flow closures and a reduced speed limit of 40 km/h will be in place during work hours for the safety of workers and motorists.
Motorists are advised to allow up to 10 minutes of additional travel time, drive to the conditions and follow the directions of signs and traffic control.
Transport for NSW thanks motorists for their patience during this time.
For the latest traffic updates download the Live Traffic NSW app, visit livetraffic.com or call 132 701.