It's hoped two way traffic will be flowing across the damaged Hwy. 402 Indian Rd. overpass by the middle of next week.
The southbound lanes were rendered impassable when a transport truck's load hit the underside of the overpass November 23 causing significant structural damage.
Three damaged concrete girders and the road deck above had to be removed.
With repairs not expected to be complete until May or June of next year, city and county engineering staff have raised concerns about snow removal and emergency services are worried about increased response times.
In cooperation with the Ministry of Transportation, a temporary bypass will be installed to allow for two way north-south traffic.
There will be one lane in both directions.
County of Lambton Public Works Manager Jason Cole says the overpass is a vital link for traffic through the city.
"We'd really like to thank the people of Sarnia, the motorists for their patience in this matter," he says. "We know that this unexpected event has caused quite a bit of disruption and we're trying to do everything we can to restore some normality to the situation."
COPE Construction is starting the work immediately with Lambton County recouping the cost from the parties responsible for the collision.
There's been no word from Lambton OPP on any charges being laid.
-With files from Briana Carnegie.