I-43 North South Freeway – South Segment
2026 Engineering Excellence Best of State
Entering Firms: HNTB Corporation and Kapur & Associates Inc.
Client: Wisconsin Department of Transportation
The South Segment of the I-43 North–South Freeway spans 3.9 miles and represents a major investment in one of Southeastern Wisconsin’s most critical transportation corridors. The project focused on improving safety, mobility, and multimodal connectivity while minimizing impacts to surrounding neighborhoods.
Engineers designed a massive new interstate upgrade while keeping open one of Wisconsin’s busiest corridors.
HNTB and Kapur collaborated to design this new megaproject. Key upgrades include expanding the freeway from four to six lanes, reconstructing frontage roads, replacing a railroad bridge, and modernizing two interchanges. A key improvement was replacing an outdated cloverleaf interchange with a diverging diamond interchange designed to improve operations, enhance safety, and extend the interchange’s service life. Replacing the active railroad bridge required constructing a new structure alongside the existing one while maintaining uninterrupted rail and freeway operations, supported by advanced geotechnical solutions.
“The design team created staging plans that carried nearly 100,000 vehicles per day through the work zone and allowed the construction work to be completed. Public involvement was intensive to stakeholders to make them aware of the schedule and closures. The team should be commended for a job well done to deliver this nearly $200 million project.”
- Awards Judge Tom Buchholz
Sustainability guided the project, with recycled pavement, balanced earthwork, and stormwater improvements that reduced sediment runoff to the Milwaukee River by more than 40 percent. Delivered on time and under budget, the project has already reduced crashes by 50 percent, setting a new standard for safe, resilient transportation infrastructure in Wisconsin.