The Princes Highway at Darkes Forest will be closed for two nights later this week between Helensburgh and Bulli Tops while work is carried out on Darkes Forest Bridge.
The work will involve lifting the bridge for the removal and replacement of bridge supports, in the hope of reducing ongoing maintenance costs. It will also ensure the structure remains safe.
The road will be closed from Helensburgh to Bulli Tops in both directions, between 7pm and 7am on Thursday 11 April, weather permitting.
Lane closures will be in place until Friday 12 April. A reduced speed limit of 40 km/h will remain in place until further notice.
Further work and road closures will be required.
Motorists can detour via the M1 Princes Motorway or Lawrence Hargrave Drive.
Residents should approach traffic controllers for access to their properties.