Work on Highway 61 along the North Shore of Lake Superior will push traffic onto a detour for about a week starting Monday.
The Minnesota Department of Transportation says the detour, between Little Marais and Illgen City, will add about 10 minutes to travel time. The highway will reopen Friday afternoon.
A contractor is flattening hills and widening shoulders on about 5 miles of Highway 61.
MnDOT engineer Dan Erickson said: "It includes culvert replacements, shoulder widening; we're going to construct new, wider ditches to drain the highway better, and we have a new bridge being constructed at Little Marais River, and then the whole five miles gets new pavement."
The road's shoulders will become twice as wide as they are now, he said.
"It is a heavily traveled road, so any extra space you can have if you have to pull over for an emergency situation is really beneficial," Erickson said.
MnDOT has spent more than $115 million in recent years on the busy two-lane road, Erickson said.
Next summer, drivers will face a detour for about three weeks. The project is scheduled to be completed by September 2014.