MANCHESTER — The business suits and briefcases of downtown Manchester give way to activewear and running shoes this evening, as the city plays host to the Cigna/Elliot Corporate 5K Road Race.

Some 5,000 runners are expected to participate in the event, which is celebrating its 20th year.

Street closings will start as early as noon as workers start preparations for the race. A portion of downtown Elm Street will close at 3 p.m. By 6:10 p.m., motor vehicles won’t be allowed on the race course, which involves Elm and Canal streets in the downtown and North End. Both the Notre Dame and Amoskeag bridges will be closed.

“At that point, downtown will be in a lock-down mode, said police Lt. Mike Hurley. That will last until about 7 p.m. Twenty-five police officers have been hired to control traffic, he said.

“It’s going to be very difficult for people to leave their business or get into their business,” he said. By 7:30 p.m., police will begin to slowly open up streets, with core downtown streets opening around 8 p.m.

Hurley suggests that north-south motorists use Union Street or city streets farther to the east; streets closer to downtown will be crowded, he said.

The main drag through the Millyard, Commercial Street, will be open, but cars will not be able to turn onto Canal Street, Hurley said.

Hurley said pedestrians and bicyclists will be allowed onto the closed streets.

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