The Sand Creek Byway in Sandpoint will open to traffic Friday.
After readying the road and removing barriers, crews opened all lanes at 9 a.m.
Crews will now turn their attention to the bike and pedestrian trail along Sand Creek.
Everything is expected to be open by mid-afternoon Friday.
The $100-million construction project took four years to complete. Crews started it in October 2008.
The 2-mile project includes six bridges, 65 retaining walls and the pedestrian-bile path.