I-39/90 Expansion Project

Illinois state line to Madison, Dane and Rock counties

Roundabout interchanges

The Wisconsin Department of Transportation (WisDOT) incorporated roundabouts at key locations within the I-39/90 Expansion Project.

Recent studies show that roundabouts provide a safe and efficient traffic flow when compared with other intersection configurations. A 2015 safety study produced by the University of Wisconsin Traffic Operations and Safety (TOPS) Lab showed that fatal and severe injury crashes decreased by 40 percent at Wisconsin roundabouts. The Insurance Institute for Highway Safety found roundabouts are safer for two main reasons:

  • Less potential for serious crashes (head-on and T-bone collisions are eliminated)
  • Low travel speeds (less severe crashes result from lower travel speeds)


Learn about the safety and efficiency of modern roundabouts, and the proper way motorists, bicyclists and pedestrians should use these types of circular intersections.


The following documents are in Adobe PDF PDF format.
(Note: Some files are large and may take longer to download depending on individual connection speeds. Users may need to zoom in to see details.)

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