Lanes on the Windang Bridge will be closed for several days throughout September.
On Wednesdays and Thursdays until the end of September Transport for NSW will be carrying out monitoring and inspection work on the underside of the bridge.
The southbound slow lane and shared footpath will be closed on Wednesdays between 7.30am and 3pm.
The northbound slow lane and shared footpath will be closed on Thursdays between 9.30am and 3pm.
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One shared path will remain open at all times for pedestrians and cyclists while the work is carried out.
Motorists are advised to allow an additional five minutes travel time when the closures are in place.
The investigation work forms part of Transport for NSW's project to add stability to the bridge.
The plan includes placing rocks at the base of the piers to reduce the erosion of sand since the sea entrance to the lake has been reopened.
The work started in August and is due to be completed by the end of the year.