The project, which began in November, has forced vehicles weighing more than 68 tonnes to use the Hexham Bridge via the M1 Motorway or Cabbage Tree Road.

Transport for NSW regional director Anna Zycki said the works were advancing and were expected to wrap up in coming months.

"Maintaining the four-lane, 23-span concrete arch bridge is no easy feat but crews have been working within the bridge's interior 35 metres above the river, installing steel plates to strengthen the expansion joints," she said.

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"Work is now progressing on fitting steel plates externally and to do this, crews are using a custom-designed lightweight access platform which is 11 metres wide and stretches under the entire width of the bridge."

Majority of the works have been carried out at night, between 7pm and 5am Sunday to Thursday. Lane closures have been required at times.

Ms Zycki said the NSW government-funded project would ensure the Hunter River crossing provided a safe and reliable journey for years to come.

"More than 19,000 vehicles a day use this essential transport and freight link between Newcastle and Port Stephens, and almost 1000 of those are heavy vehicles," she said. "This work is helping support eight full time positions and is also providing employment for another eight companies, including steel fabricators and spray painters."

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