WORK has started on the $16.5 million upgrade of the overhead rail bridge at Lily Street, Allawah.
Oatley MP Mark Coure said the work would be undertaken in multiple stages by Sydney Trains.
The upgrade will comprise one northbound lane and three southbound lanes, including a left-turn lane, right-turn lane and another for through traffic.
"The existing overbridge has reached the end of its serviceable life and needs to be replaced with a new one in order to address congestion issues and improve safety for motorists and pedestrians," Mr Coure said.
"The community overwhelmingly supports increasing the capacity on the bridge, especially during the morning and afternoon peak times."
Mr Coure said the work should be completed by November 2017 and access to Allawah railway station would be maintained until then.
"There will be some planned road closures during the construction period and a comprehensive traffic management plan has been implemented to ease distributions and manage traffic flow," he said.
The design of the four-lane bridge was based on traffic studies by Hurstville Council and has the support of Kogarah Council.
Residents and businesses have been notified and further project information can be found at transport.nsw.gov.au/sydneytrains/maintenance.