Motorists driving along Interstate 470 have seen the warning for a couple weeks now – a large orange sign announcing lane closures later this month at the northern end of I-470 likely to cause significant delays.

Specifically, the Missouri Department of Transportation will make both directions of I-470 go from two lanes to one between 39th Street in Independence to just south of the Little Blue River. Crews are to make repairs to the bridges above Interstate 70, U.S. 40 and the Little Blue River.

The project is expected to take a couple months. When exactly that begins has not yet been finalized, but MoDOT has been posting mid-August, and department spokesperson Lairyn McGregor said that's still the case. As of Tuesday, the taregt date was Aug. 13. Work should be done by November.

MoDOT has been warning motorists to anticipate delays of up to 50 to 75 minutes or more during peak hours while crews work on the bridges – “Delays like you've never seen before,” it has said – so motorists should plan ahead, leave earlier if necessary find alternate routes. When the highway pinches to one lane, motorists are asked to use the zipper merge method.

First though, MoDOT plans to close the left (inside) lane in both directions this weekend for paving work along the shoulders. The short-term highway squeeze is scheduled for 8 p.m. Friday to 5 a.m. Monday. MoDOT had planned to do this last weekend, but rain the forecast postponed work again. MoDOT did work on the outside lanes earlier this summer.

“They're paving the shoulders so when it comes time to shift traffic, it can withstand (vehicles' weight),” McGregor said. When the bridge repairs begin, she said, “is pretty contingent on this getting done.”

Jacob Wilson, MoDOT engineer, said the bridges over the Little Blue River and U.S. 40 will get joint replacements. The bridges over I-70 will get complete overlays.

Ramp closures will be contingent on the areas of work, but MoDOT says the outside ramps at the I-70/I-470 interchange should not be affected, and at one point all four inside loop ramps will be closed.

MoDOT estimates an average of 90,000 vehicles pass daily through that portion of I-70, and 70,000 use I-470 in that area.

These upcoming bridge repairs are part of MoDOT's overall project dating back to last year to rehab all of the bridges that cross I-470 and extend their lifespan. Last year, I-470 traffic west of Pryor Road in Lee's Summit was alternately shifted onto one set of lanes, allowing crews to work on three bridges at a time in the same direction. The I-470 bridges above Lakewood Boulevard/Bowlin Road had been scheduled to be part of this upcoming project, McGregor said, but those have been pushed back to next year.

The bridge repairs come at a time when MoDOT also is rebuilding three no-ramp bridges over I-70 in Independence – at Pittman Road, Crysler Avenue and Phelps Road. That has caused some headaches for drivers in Independence – headaches that could be amplified with the I-470 bottleneck.

“There's a lot of bridge work going on in the Kansas City area (more repairs are taking place near the Grandview Triangle), but a lot of them were built around the same time,” McGregor said. “They're figuring it's better to try to get them all done in one quick swoop.”

McGregor said crews anticipate being finished with the I-470 bridges before November – work contracts also end after Nov. 2 – and the extra weeks are for contingency.