Illinois Route 23 Interchange along I-90 Improves Access


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  • Award Winning
  • Engineering
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  • Roadways + Interchanges
  • Transportation


  • McHenry, Illinois

I-90 is the only interstate that cuts through McHenry County and the new interchange at Illinois Route 23 is the county’s first. The long-awaited interchange intersects at Illinois Route 23 on the Jane Addams Memorial Tollway (I-90) and features roundabouts and all-electronic tolling at the I-90 exit and entrance ramps to improve safety and mobility.

The interchange gives the City of Marengo, a rural community 60 miles west of Chicago, and surrounding communities direct access to I-90, which has the potential to stimulate economic growth along the Illinois Route 23 corridor. This strategic location provides much-needed access in the middle of what was a 17-mile gap between the two closest interchanges on I-90.

The project is the result of years of planning, study, and cooperation through a partnership among the Illinois Tollway, the Illinois Department of Transportation, the McHenry County Division of Transportation, and Marengo. After multiple studies, the Illinois Tollway and its agency partners moved forward with a partial cloverleaf interchange – a standard interchange layout. What makes this interchange unique are the roundabouts at the ramp termini. Roundabouts are in use throughout Illinois, but this is the first use of roundabouts at an interstate interchange in Illinois.

HR Green and its team assisted with the planning stages and provided the Phase I and Phase II engineering services. The Phase II engineering services included contract plans, cost estimates, and specifications to meet not only Illinois Tollway requirements but those of partner agencies, as well. This included developing a robust public involvement program, using 3D video to educate customers, and showing how oversized, overweight trucks would navigate the roundabouts.

HR Green, the Illinois Tollway, and Stantec won the Honor Award and the Judges Choice Award in ACEC Illinois’ 2021 Engineering Excellence Award Competition for the Illinois Route 23 Interchange on I-90 project. The project also won a National Recognition Award in the ACEC National competition.


American Council of Engineering Companies – National Recognition Award. ACEC Illinois – Honor Award and Judges Choice Award.

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