The Redbank Plains Road overpass at Blackstone has partially reopened to westbound traffic on Monday.
The overpass will remain closed to eastbound traffic until bridge repairs are undertaken.
The bridge over the Cunningham Highway was temporarily closed earlier this month for safety reasons while assessments could take place after it was struck by a heavy vehicle.
The vehicle also struck the Cunningham Highway bridges over Aberdare Street at Dinmore.
Transport and Main Roads Metropolitan Regional Director Patrick Dennehy said the Department of Transport and Main Roads (TMR) was continuing to monitor the structure.
“Following the incident, structural engineers assessed the bridges and determined that significant damage had been sustained by two of the Redbank Plains Road bridge girders,” he said.
“Following further assessments, TMR is now pleased to advise the Redbank Plains overpass will reopen to westbound traffic with one lane operational.”
Dennehy said motorists travelling east would still be required to seek alternative routes.
“Unfortunately, due to the nature of the damage to the eastbound lane on the Redbank Plains overpass, it will not be able to carry traffic until repair work is completed,” he said.
“TMR is currently undertaking design for the repair work and can’t yet provide a time frame for when the bridge will fully reopen.
“I would like to thank the travelling public and local community for their patience while these important works are undertaken.”
Some heavy vehicle restrictions will remain in place until further notice.