NASCAR’s Chicago Street Race will affect traffic on DuSable Lake Shore Drive more than previously expected.

With less than three weeks until the big event in and around Grant Park, Chicago transportation officials say drivers will have to merge along a 19-mile section of DuSable between North Avenue and 47th Street.

The “merging taper” will ease congestion downtown, officials said Tuesday.

“It would be irresponsible to let four lanes come all the way up to a heart of closure,” said Christopher Pettineo, manager of emergency management services at the Office of Emergency Management and Communications.

The merger will impact southbound drivers the longest.

For seven days, from June 28 to July 4, southbound traffic on DuSable will be reduced to two lanes at North Avenue and to one lane at Chicago Avenue. All traffic must exit at Grand Avenue.

Northbound travel on DLSD will be affected for only the two days of race weekend, July 1-2.

Northbound traffic will be reduced to two lanes at 47th Street, and to one lane near 31st Street. All traffic must exit at I-55, except for drivers headed to the museum campus. Those drivers can continue to the 18th Street exit.

Tom Carney, first deputy commissioner of the Chicago Department of Transportation, said drivers should plan ahead, just as they would for any other major event downtown, such as Lollapalooza or New Years Eve.

“Really this event is no different,” Carney said. “While it’s the first time the city had this event, plus some different roadway closures, … the philosophy is the same about planning ahead.”

One difference, he said, is the wider availability of resources available online to help the public to plan their travel. The city also plans an extensive array of signs to warn and direct drivers drivers.

Officials outlined detours to the museum campus, where representatives of the various tourist destinations had expressed concern about a dip in attendance due to road closures and congestion.

Those routes mostly use the Stevenson Expressway and South DuSable Lake Shore Drive. Detours to Navy Pier from the South or West sides use the Ohio Street exit on the Kennedy Expressway.

Pettineo said OEMC has been communicating extensively with leadership on the museum campus. Some museums have changed their schedules in response to the race.

“I’ve had so many meetings with all of our partners” at the museums, Pettineo said. “It’s really great to see it come together. It was a little painful at first.”

NASCAR estimates 100,000 people will attend the races over the weekend. Last year, then-Mayor Lori Lightfoot reached a three-year deal with NASCAR to hold one race a year downtown.

Asked if the city is willing to repeat all of the work for the NACAR race expected next year, Pettineo said: “I think I can speak for everyone that this is a first-time event, and if we didn’t get the planning right the first time around, then shame on us.”

“And that’s why we stuck to this schedule. It was rigorous: six committees in addition to general city meetings, countless breakout meetings,” he said. “We’re not going to drop the ball. We can’t. We’re Chicago.”