Works have begun on the construction of Thalaba Bridge at Dungog — with traffic diverted away until November.
The $16 million project is one of 23 bridges being replaced around the local government area, in a bid to improve safety.
The current timber structure and design will be demolitions and replaced with a new concrete bridge and road approaches.
Alison Road is closed from the Clarence Town Road and Pin Brush Road intersections for the duration of the works, but residents will continue to have access.
Signage is in place to direct motorist through the diversion via Clarence Town Road to Clarence Town, Alison Road North to Stroud Hill Road and South Pine Brush Road.
Dungog Shire Council Mayor John Connors says the project would build new, stronger, and more resilient river crossings shire-wide.