Drivers are advised to allow extra travel time on Rangari Road this week as initial works begin between Manilla and Boggabri.
A reduced speed limit of 40km's per hour will be in place for the full week as geotechnical investigations take place between the 18th and 22nd January.
Traffic controllers will be in operation, and the road will be reduced to one lane at various testing locations between 7 am to 5 pm daily.
Community members and local Council's have been calling for this work to be done since before 2015 when Regional Development Australia did a cost-benefit analysis for the project.
Jaime Chaffey, Mayor of Gunnedah Shire Council said they have been working in cooperation with Tamworth Regional Council for several years to get funding and green light the upgrade.
"Many residents from both of the local government areas use this road on a daily basis," Mr Chaffey said, "It's a very important road and its in poor condition."
Funding was announced by the state government last year however Gunnedah Council says it's not enough to seal the entire road and the shortfall will land within their Shire.
The long-awaited upgrade will both seal and widen 20km's of the road from 3.8kms east of the Gunnedah / Tamworth local government area boundary to the Gunnedah / Narrabri local government area past Wean Road.
Shovels are expected to hit the ground for the main road work from the middle of this year.