One of the busiest freeway ramps in the metro area will shut down for two weeks late Sunday, putting drivers on a 15-mile detour.

The Minnesota Department of Transportation will shut down the ramp in downtown Minneapolis from eastbound Interstate 394 to eastbound Interstate 94 that deposits traffic into the Lowry Hill Tunnel, which is under construction.

The prescribed rerouting will send motorists on a long detour south on Hwy. 100, east on the Crosstown and north on I-35W.

"We realize that is quite a distance," said spokesman David Aeikens. "We are trying to keep drivers on state highways. We hope they don't go downtown."

Construction on I-94 has already made this a long summer for Kate Stephens, who lives near the I-394 and Penn Avenue exit just west of downtown Minneapolis. She uses the ramp to commute to her job in Eagan and just about everywhere else. With all the road construction this summer, her drive to work takes about an hour. With the I-394 ramp closure she's facing the prospect of spending even more time in heavy traffic.

"It's going to be a nightmare to get into work," she said. "I'm going to ask my boss if I can work at home for the next two weeks."

Some drivers have already started scouting out alternate routes. One of the most talked about on social media has drivers jumping up to Hwy. 55 and using the ramp there to access eastbound I-94. That would be a viable option under normal circumstances, but that ramp also is closed until early September.

Others have suggested exiting I-394 at Dunwoody Boulevard and following Hennepin Avenue to eastbound I-94. But that route past the Walker Art Center already sees its share of bottlenecks and traffic as 31,000 vehicles use Hennepin and Lyndale avenues each day, according to city and state traffic counts.

Minneapolis officials are bracing for extra traffic on those routes and from motorists snaking through downtown Minneapolis and getting back on I-94 at 6th Street by the Vikings' stadium. The city plans to monitor traffic and adjust signal lights if necessary. It also plans to step up efforts to keep delivery trucks and cars from stopping along curbs and blocking lanes on heavily traveled streets.

But really, officials are not totally sure what to expect. "Estimating traffic as a result of the ramp closure is a challenge because the detour route is so far upstream of the closure," said spokeswoman Sarah McKenzie.

Metro Transit said the ramp closure will likely affect its State Fair express service from the County Road 73 park-and-ride lot in Minnetonka and the one at Dunwoody in downtown Minneapolis.

Buses will be rerouted and trips may take longer. But since buses can use shoulders to bypass traffic, delays may be modest, said spokesman Drew Kerr.

"As a precautionary step, we are adding some extra buses into the rotation at these sites when possible," he said.

Normally 23,000 drivers use the I-394 ramp daily. Should motorists follow the posted detour, that no doubt will put extra pressure on Hwy. 100, which has become a workhorse this summer as it also has absorbed drivers diverting around a closure on Hwy. 169. In January, MnDOT shut down Hwy. 169 between Crosstown and Lincoln Drive to rebuild the Nine Mile Creek bridge. In the process, the agency directed the 90,000 motorists who normally cross the bridge on the Edina-Minnetonka border each day to use I-494 and Hwy. 100. That project is on schedule but won't be finished until October, MnDOT said.

"Highway 100 is three lanes and we think it can handle it [the extra traffic]," Aeikens said. "We are not saying you'll have a clear unimpeded path. There will be more cars, but we would not put it there if we didn't think it could handle it."

The I-394 ramp shutdown is part of a summerlong project along I-94 that spans 9 miles between Nicollet Avenue in Minneapolis and the Hwy. 252 interchange in Brooklyn Center. MnDOT is repairing more than 50 bridges and repaving and rehabilitating the freeway that was originally constructed in the 1980s. That project will run through October, but work in the Lowry Hill Tunnel will wrap up by mid-September. The I-394 ramp to eastbound I-94 is set to reopen in time for morning rush hour on Aug. 29.

In the short term, drivers like Stephens are bracing for two weeks of major headaches.

"I'm not looking forward to it," she said. "I've got lots of podcasts. It's the only way to endure this."

Because of an error from the Department of Transportation, an earlier version of this story stated the detour would start late Monday.

Tim Harlow • 612-673-7768