Rebuilding a busy stretch of Iowa Street and expanding two of its major intersections in the coming years will cost millions of dollars and cause plenty of traffic delays, officials acknowledge.

But they’re looking forward to the payoff down the road.

“Things will move better,” said Chuck Soules, the city’s director of public works.

Two projects — one announced Friday, and another to have its schedule determined next week — will be expected to affect travel for more than 60,000 vehicles per day, both by causing delays during construction but easing flow once it’s done.

The projects:

• Adding various turn lanes at the intersection of Iowa and 15th Street/Bob Billings Parkway, part of a larger $6 million reconstruction of Iowa from Harvard Road to the Irving Hill Road overpass scheduled for 2013. Tuesday night, Lawrence city commissioners will discuss a recommendation to close 15th Street/Bob Billings at Iowa Street for the summer of 2013, for reconstruction.

• Adding additional left-turn lanes along 23rd Street and Clinton Parkway at Iowa, a project that would expand the intersection — already the busiest in town, with about 60,000 vehicles per day — to provide dual left-turn lanes in all directions. The Kansas Department of Transportation announced Friday that it would invest $500,000 in the estimated $1.5 million project, expected for construction in 2013 or 2014.

Both projects will be expected to do more than ease traffic flow, as engineers envision changes to reduce the frequency of accidents at several trouble spots.

Widening Iowa Street from Yale to Irving Hill, for example, will add a center turn lane north of 15th — virtually eliminating rear-end accidents now considered commonplace involving vehicles waiting to turn left onto University Drive and Stratford Road, said David Woosley, the city’s traffic engineer.

“That should make a big difference,” he said.

And the project on 23rd Street will reconfigure the free-flowing right turn for westbound traffic turning north on Iowa, at the corner that is home to Freddy’s Frozen Custard & Steakburgers. The goal will be to eliminate the ongoing conflicts caused by traffic merging along Iowa, in which cars accelerating to go north mix in with vehicles slowing down to enter the shopping center.

“We had 26 crashes there in a two-year period,” Woosley said, confident that that the project’s final design would address the problem. “If there’s any traffic coming, you will have to stop. It will be a much sharper turn. (Even if there’s no traffic approaching on Iowa), you will have to slow down, almost to the point of stopping.”

Both projects also promise to spur plenty of short-term inconvenience.

For much of 2013, traffic will be down to one lane in each direction along Iowa, from Harvard to the overpass. Tuesday night, commissioners have two choices for handling the intersection at 15th/Bob Billings:

• Close 15th and Bob Billings at Iowa, forcing traffic onto detours but limiting reconstruction to the period between the close of Kansas University’s spring semester and opening of the fall semester. Traffic on Iowa would remain limited to one lane in each direction, but would not have to stop at the intersection.

• Keep the intersection open, which would spur lengthy delays for traffic passing through the intersection and likely more than doubling the length of time to get that part of the job done — and likely at a higher cost, Soules said.

“It’s going to be a nightmare if we need to keep that area open, and construction needs to go through a portion of the school year,” he said.

The commission meeting is set for 6:35 p.m. Tuesday at City Hall, Sixth and Massachusetts streets.