The Oxley Highway in Gunnedah will be closed and a temporary detour put in place from Monday.
Work on a new roundabout means the highway will be closed near the intersection of Boundary Road and traffic will be diverted onto and off the two southern legs of the roundabout.
Transport for NSW said the detour would be in place for two weeks and was suitable for heavy vehicles. They are currently being redirected to Wentworth Street, which connects with Bloomfield Street.
Work will be carried out from 7am-6pm on weekdays and 8am-1pm on Saturdays, weather-permitting. Traffic control and a reduced speed limit will be in place.
Following these works, revised traffic arrangements will be put in place until the roundabout and associated link roads are completed.
Transport for NSW north region director Anna Zycki said the new heavy vehicle roundabout should be in use by the end of July.
The project was originally anticipated to be completed last year but has been set back by land acquisition issues, supply delays due to COVID-19, and wet weather.
"Work to carry out final asphalting of the road surface and the roads leading into the roundabout will be completed in the coming weeks," Ms Zycki said.
"The roundabout is expected to be complete and operational with temporary lighting by the end of July, and permanent lighting is expected to be installed by the end of September."