Commuters in the south metro who use Cedar Avenue to cross the Minnesota River will have to find alternate routes beginning Friday night, when a bridge repair project expected to last the rest of the month begins.

Starting at 8 p.m., the Minnesota Department of Transportation will shut down the southbound lanes of Cedar Avenue between Old Shakopee Road and Hwy. 13 for 10 days to paint the 36-year-old bridge, install new guardrails and fix bridge joints. The closure will last through June 15. Action will then shift to the northbound lanes, closed June 19-30.

Meanwhile, sections of two other major metro highways will shut down, but only for the weekend. Northbound Hwy. 100 from Crosstown to Interstate 394 and southbound I-494 from the Fish Lake interchange to 394 through Maple Grove and Plymouth will be closed from 10 p.m. Friday to 5 a.m. Monday.

Taking out one of the few river crossings in the south metro will send thousands of motorists onto the prescribed detour along Interstates 35E and 494. It's likely that I-35W also will see increased traffic, as was the case two summers ago when the Hwy. 169 bridge was out of commission, said Kirsten Klein, a MnDOT spokeswoman.

"People will need to be patient," Klein said.

North-south thoroughfares such as Lexington Avenue and Pilot Knob Road may see extra traffic as drivers use those routes to connect with 494 to cross the river.

MnDOT considered having traffic share one side of Cedar Avenue while the work is done, but "that would have lengthened the project to six weeks instead of 20 days," Klein said.

The Metro Red Line will run at 30-minute intervals instead of the normal 15 minutes on weekdays. Express buses — especially those running between downtown Minneapolis and Apple Valley and Eagan — also will be on detour, and riders should plan on them running late, said Robin Selvig, a Minnesota Valley Transit Authority spokeswoman.

Selvig said MVTA will have its entire fleet on the streets and will have buses parked at strategic locations to fill in should routes start lagging severely. "Take earlier buses and arrange for flexible work schedules if possible," she said.

In the west metro, northbound Hwy. 100 drivers will be detoured west on the Crosstown, north on Hwy. 169 then east on 394 during this weekend's closure.

Drivers on southbound 494 will be routed from the 494/694/94 split over to Hwy. 169, then south to 394, then west back to 494. MnDOT will open the ramp from westbound 394 to southbound 494 to accommodate detoured traffic, MnDOT said.

In addition to Cedar Avenue, Hwy. 100 and 494, motorists will see cones and detours on Hwy. 13 between 2nd Street and Lexington Avenue in Mendota. Both ramps from 94 to Snelling Avenue are closed, and earlier this week Snelling was closed between 94 and University Avenue.

Other big construction zones include I-35E between Little Canada Road and downtown St. Paul, Hwy. 5/W. 7th Street between Fort Snelling and Davern Street, and Hwy. 10 near Armstrong Boulevard in Ramsey.