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Between 2018 and 2019, MnDOT installed a lane constrictor design at 66 side-street, stop-controlled intersections in Minnesota. The lane constrictor design narrows the lane width for mainline approaches via a striped median with centerline rumble strips. By narrowing the mainline lane, the goal of this design is to encourage mainline traffic to slow down as it approaches the intersection. The striped median also provides greater separation between mainline directions and draws more attention to the location of the intersection. Following the installation of lane constrictors at MnDOT intersections, overall crash rates have seen little change but there have been decreases in fatal and serious injury (KA) as well as fatal and all injury (KABC) crash rates. These results indicate the addition of lane constrictors have a positive impact on crashes by reducing the severity of crashes, swapping injury crashes for property damage only crashes.

Modern roundabouts have been shown to be one of the safest methods of control for at-grade intersections. An evaluation of traffic safety at roundabouts published by MnDOT in 2017 shows substantial decreases in fatal and serious injury crashes at intersections after installation of a roundabout. Despite these benefits, concerns have been raised from citizens, commercial motor vehicle (CMV) drivers, and other stakeholders about the propensity for roundabouts to cause more rollover crashes for larger vehicles. The purpose of this evaluation is to further evaluate the safety of heavy commercial vehicles at roundabouts, investigate whether rollover crashes are more likely to occur at roundabouts, and break down the most common characteristics for CMV crashes at roundabouts in Minnesota. This report includes the results of an analysis comparing roundabouts to signalized intersections. The results of this evaluation indicate that roundabouts continue to be one of the safest forms of intersection control for heavy commercial vehicles, especially when compared to traffic signal control. Although roundabouts have experienced a greater number of rollover crashes compared to intersections with traffic signal control, their installation results in a decrease in high-severity crashes.

Between 2016 and 2021, MnDOT installed retroreflective signal backplate borders at 116 signalized intersections in Minnesota. Retroreflective signal backplate borders are intended to further increase visibility of the signal head both during the day and at night. The goal of installing retroreflectivity to backplates is to reduce crashes at the intersection by drawing more attention to the current phase of the signal. Backplates with retroreflective borders are listed as a Federal Highway Administration Proven Safety Countermeasure with a listed safety benefit of a 15% reduction in total crashes. With the installation of retroreflective signal backplates on MnDOT signals, the changes in crash rates were not found to be statistically significantly different from similar locations that did not have retroreflective signal backplates. These results indicate there has been little impact on crash rates in the few years after the installation of retroreflective signal backplates.

Between 2010 and 2020, 49 Reduced Conflict Intersections (RCIs) were installed on Minnesota Department of Transportation (MnDOT) roadways. The RCI is an alternative intersection layout that is intended to provide safety benefits by limiting the number of points within an intersection that two or more vehicle paths might intersect. Both a before-after analysis at RCIs and a cross-sectional analysis comparing RCIs to untreated intersections were conducted. With the installation of an RCI, both analyses yielded statistically significant decreases in fatal and serious injury crashes, angle crashes, and fatal and serious injury angle crashes. Statistically significant increases in rear-end crashes were found. Both analyses showed no significant changes to sideswipe crashes or total crashes. Based on these results, severity shift in crashes has been seen at the RCIs in Minnesota. The overall number of crashes have not changed, but the high-severity crashes have been reduced while property damage crashes have increased. The large decreases in severe crashes at RCI locations indicate the RCI can be an effective safety treatment.

By the end of 2022, nearly 450 roundabouts were installed on Minnesota roadways. An evaluation of traffic safety at roundabouts published by MnDOT in 2017 showed substantial decreases in fatal and serious injury crashes for all users at intersections after installation of a roundabout. The safety effects of roundabouts are largely due to geometric design practices that reduce the speed of motorized vehicles as they approach and travel through the intersection. The purpose of this evaluation is to determine if the safety effects seen in the 2017 evaluation still apply to roundabouts with higher levels of use by pedestrians and bicyclists. This evaluation conducts a before-after analysis of 95 roundabouts in Minnesota and an analysis comparing roundabouts to untreated intersections. With the installation of a roundabout, this study finds that the before-after analysis results in a 40% decrease in all severity injury crashes for all roadway users, a 70% decrease in fatal and serious injury crashes for bikes and pedestrians, and a 15% decrease in total pedestrian bike and pedestrian crashes. The results of the comparison analyses suggest roundabouts have better safety performance than through-stop and traffic signal-controlled intersections and similar safety performance to locations with all-way stop control. The results of this evaluation thus indicate that roundabouts can be an effective safety treatment for pedestrian and bicycle crashes.