3 new diverging diamond interchanges are coming to Appleton. Here’s what to know.

APPLETON — In an effort to increase traffic safety, the Wisconsin Department of Transportation is constructing three new diverging diamond interchanges as part of the Interstate 41 expansion project.

The I-41 project, which will expand 23 miles of I-41 between Appleton and De Pere from four lanes to six lanes, started construction in the spring and is scheduled to be completed in 2030. As part of the construction, multiple intersections will be updated, including the three diverging diamond interchanges.

Mason Simmons, traffic safety engineer for the Wisconsin DOT’s northeast region, said there is currently only one diverging diamond interchange in northeastern Wisconsin, located at State 441 and South Oneida Street in Appleton. It was constructed in 2018.

Here is what to know about the new interchanges:

What is a diverging diamond interchange?

It is a type of interchange used to connect a freeway and a major roadway. When exiting the freeway, motorists briefly travel on the left side of the road, which allows for left turns that do not require stopping or crossing a lane of oncoming traffic, according to the DOT. When crossing through a diverging diamond interchange, the road temporarily operates similarly to a one-way street. Navigation is made simple by traffic signals, road markings and overhead signs.

Simmons said a the design “eliminates those left-turn, T-bone-type crashes,” and can be a good option for areas with a lot of left-turning traffic off the freeway.

It’s a relatively new type of traffic configuration. The first diverging diamond interchange in the United States was built in Missouri in 2009.

While they are becoming increasingly common, they are still relatively rare in Wisconsin. Aside from the one in Appleton, there are two near Janesville and one in Beloit, all off Interstate 39. Another diverging diamond interchange was recently constructed off I-43 in Brown Deer. Simmons said there are some in northwestern part of the state.

Where will the new interchanges be located?

The three new diverging diamond interchange will be located at I-41 and State 15, I-41 and Richmond Street, and I-41 and Ballard Road.

When will construction take place on the new interchanges?

Construction is scheduled to first begin on the interchange at I-41 and State 15 in early 2025, Simmons said. It will be followed by the I-41 and Ballard Road interchange. The two projects will be staggered, with construction planned to take up much of the year, Simmons said.

The third one, at I-41 and Richmond Street, is scheduled to begin construction in 2026.

Why are each of the new diverging diamond interchanges being constructed?

According to the Wisconsin DOT’s website, all three of the new interchanges have the goal of accommodating higher volumes of traffic and increasing safety.

Additionally, the one at State 15 will increase the merge distance for the I-41 northbound entrance ramp, and the one at Ballard Road “will require less land from adjacent property owners,” the DOT website states.

How much safer is a diverging diamond than other types of interchanges?

National data collected from interchanges five years prior to and five years after construction of a diverging diamond interchange has found an 80% reduction in injury crashes, Simmons said.

They also improve safety for more than just motorists.

“They allow us to enhance pedestrian and bicyclist safety as well,” Simmons said. “A lot of the time, we’re able to simplify the crossing maneuver for the pedestrians and then put them in a refuge area to protect them from oncoming traffic through the turning vehicles.”

Contact Kelli Arseneau at 920-213-3721 or karseneau@gannett.com. Follow her on X, formerly Twitter, at @ArseneauKelli.

This article originally appeared on Appleton Post-Crescent: What to know about new diverging diamond interchanges on I-41 in Appleton