Floodproofing on the Oxley Highway will finish a year later than expected after significant delays.
The $5 million-dollar upgrade of the Hoss Causeway between Gunnedah and Tamworth was originally scheduled for completion in late 2018 but is now earmarked for the end of this year.
Tamworth MP Kevin Anderson said the project near Carroll had been delayed by "problems associated with the culverts" and his office had been "inundated with phone calls" as drivers have been "forced to use a side-track since Christmas while waiting for this causeway to be fixed".
A spokesperson for Roads and Maritime Services (RMS) told Australian Community Media there had been a "temporary halt" but the project was now expected to be completed in December "weather permitting".
"The solution agreed with Gunnedah council requires culvert replacement and work will begin next week to remove the existing culverts. This will minimise the impacts of flooding if it occurs," they said.
"The supplier will start work this month to manufacture replacement culverts. This is currently expected to take four months, however Roads and Maritime Services is working with council and the supplier to expedite this process.
"Finding a suitable long term solution was vitally important and motorists are thanked for their patience during this time."
Mr Anderson said the "important upgrade" was "vital for the efficiency and productivity of heavy freight movements" and the delay impacted Higher Mass Limits vehicle access.
"When this project is completed the Hoss Causeway and Oxley Highway will be a safer roadway as well has having greater flood security," he said.
"I know it's incredibly dry at present, but when a change in the weather patterns finally comes along, we need to be ready. This section of roadway floods quickly and closes the highway which is a problem for this very busy road.
"I am looking forward to seeing workers back on the job and finishing the Hoss causeway upgrade."