Concrete roundabouts solution to multiple crashes in Mankato

Between 2011 and 2013, the Highway 22 intersections at Adams Street and Madison Avenue in Mankato had the highest crash rating in MnDOT District 7, an area that includes 13 counties in south central Minnesota. Studies recommended roundabouts at the two intersections to improve safety and decrease traffic delays. Flashing yellow-left-turn arrow signals and sidewalk improvements also were recommended. The intersections were built simultaneously in a very condensed time frame. Construction started on June 9 and the project opened for traffic on August 25. “High early” concrete was used in all of the paving to expedite construction.

MnDOT partnered with the City of Mankato and Blue Earth County to schedule the construction detours to have as a little disruption to business and residents as possible. They also had to factor in the increased traffic due to the Minnesota Vikings training camp and the late summer return of thousands of college students to the area.

Project Dates

June 2014 through August 2014

Project Details

33,392 square yards of concrete pavement and 54,100 square feet of concrete sidewalk were placed, and 10,700 lineal feet of curb and gutter. Despite a significant rain delay the third week of June, the project was completed ahead of schedule.


Owner: MnDOT
Design Engineer: TKDA
Public Communications: Richardson, Richter & Associates, Inc., St. Paul
General Contractor: Mathiowetz Construction, Sleepy Eye
Concrete Contractor: Hoffman Concrete, Inc., Mankato
Ready Mix Supplier: Cemstone, Mendota Heights

For more information about this project, call Glen Coudron, project manager, Minnesota Department of Transportation, 507-304-6165, or email him at This email address is being protected from spambots. You need JavaScript enabled to view it.

Download the Highway 22 Roundabouts case study.