The news is going from bad to worse for commuters already exasperated by a long summer of downtown construction. A huge new road project on Interstate 35W through south Minneapolis is starting. On Monday.

Sorry, drivers.

The $239 million reconstruction is hardly the biggest in terms of budget, but the massive scope may be one of the most disruptive and prolonged in recent years. Transportation Commissioner Charlie Zelle called it a “complicated but significant project” during a show-and-tell for media representatives Thursday. It will last four years and be carried out in five phases.

“It will be tough [on drivers],” said Scott McBride, a Minnesota Department of Transportation engineer.

That might be an understatement in a season already rife with congestion, lane shifts, bridge closures and detours.

The project between downtown Minneapolis and 46th Street begins while drivers are still dealing with construction in the Lowry Hill Tunnel and on Interstate 94 out to Brooklyn Center, which won’t be done until mid-September. Bridges on the local streets of Portland and Cedar avenues between 28th and Lake streets are out of service until November.

If there is a saving grace, drivers on the state’s most used freeway won’t feel a huge impact until spring. But motorists on city streets will start feeling it just after Labor Day.

The Franklin Avenue bridge over I-35W will close this fall until April. The closure of that east-west crossing will make commutes a lot more challenging. Alternates include 26th and 28th streets. But not 38th Street. That overpass also will shut down during phase one.

Also closing this fall is the ramp from westbound I-94 to 11th Street, and the Portland Avenue bridge over I-94, which will be closed for eight weeks starting in September. It was just a few years ago that Portland drivers gutted out a summerlong detour as MnDOT put a new deck on that bridge. This time the agency will remove one pier and rebuild it to accommodate a new auxiliary lane to carry traffic from eastbound I-94 down to Lake Street. The work will be done on the underside of the bridge, but project manager Scott Pedersen said MnDOT can’t allow traffic on the bridge while the work is being done.

The entire I-35W rebuild includes reconfiguring the flyover bridge from northbound I-35W to westbound I-94, building a new transit station in the center of I-35W at Lake Street and replacing or refurbishing 18 bridges along the 3-mile segment. It also includes new exits at Lake and 28th streets, adding a MnPass lane between 26th and 46th streets, and replacing the original pavement, which was put down in 1965 and doctored up all these years.

Next spring when phase two gets underway, the I-35W flyover ramp carrying traffic to west I-94 will close for the duration of the project. So will the ramp from east I-94 to south I-35W. And the real kicker: Northbound I-35W to the downtown exits — namely 5th Avenue and 11th Street — also will shut down, forcing drivers to head over to 3rd Street or Washington Avenue to access downtown. Ouch.

MnDOT says it will add extra lanes on Interstate 394 between downtown and Hwy. 100 next spring to help with the traffic crunch. Crosstown also will be re-striped with a third lane, McBride said.

Misery will spread to south Minneapolis neighborhoods next spring when lanes on Park and Portland avenues now reserved for parking are dedicated to buses during peak travel periods. The lanes will give transit vehicles access to I-35W when downtown exits are closed.

“We all have to be ready for construction. There is no soft-pedaling that,” said Hennepin County Commissioner Peter McLaughlin. In the end, however, he said the finished product will give Minneapolis “a 21st century transportation system.”

That system will include a flashy transit station at Lake Street and a new Bus Rapid Transit line connecting Minneapolis to Burnsville and putting transit in the fast lane. The rebuilt I-35W also may serve as a blueprint for upgrades being planned for I-94 between downtown Minneapolis and downtown St. Paul, and I-35W north of downtown Minneapolis out toward Roseville.

“This will be a model freeway,” Minneapolis Mayor Betsy Hodges said, when it’s finished in 2021.