Work will be carried out Sunday to Thursday between 7pm and 5am for the next five weeks, weather permitting.

Lane closures and a 40km/h speed limit will be in place during working hours.

The stage one improvements involve installing traffic lights on the eastbound approach to the roundabout to reduce westbound queues.

"The traffic lights are expected to better manage traffic in the afternoon peak by providing more frequent gaps between vehicles, which allows more westbound vehicles to travel through the roundabout," a Roads and Maritime Service spokesperson said.

"Traffic queue detectors will be installed on the highway to trigger these lights, which will stop eastbound traffic when there are westbound queues and also manage delays for eastbound motorists."

Work also includes extending the left turn lane on Cessnock Road by about 100 metres.

"This will improve traffic flow and reduce the queue length on Cessnock Road in the morning peak by providing additional lane capacity for traffic travelling through the roundabout to Church Street," the spokesperson said.

The NSW Government has funded the $1.5 million upgrades to improve travel times in the morning and afternoon peaks.

"This first stage of work will improve traffic flow in the short term while work continues on a design for additional changes for the roundabout," the spokesperson said. "The community and key stakeholders will be invited to comment on additional proposed changes for the road network later this year."