The roundabout at County Road 42 and County Road 43 (Banwell Road) will be open for east and westbound traffic by Thursday's afternoon commute.
The busy thoroughfare has been closed since mid-June to complete the $22-million project.
"Traffic won't be able to travel north or southbound out of the roundabout and you won't be able to get into the roundabout from the north or south direction," said Allan Botham, County of Essex Director of Infrastructure.
The roundabout is opening slightly ahead of schedule but there could be intermittent closures in the coming weeks as traffic lights are installed and other finishing touches are completed. The north and southbound entrances will be open before Christmas.
"This will be so much more efficient for people getting in and out, to businesses to residents. We've got lots of growth coming," said Warden Hilda MacDonald. "It just makes commuting easier for people, which makes them happy, which makes them drive in a better fashion."
Phase 3 of County Road 42 corridor reconstruction will begin in 2025. It includes the construction of a roundabout at the intersection of County Road 42 and Manning Road.