The annual number of near-crash events at test sites equipped with intersection collision warning systems in Minnesota decreased by approximately 26 percent.

Evaluation of intersection collision warning systems (ICWS) in Minnesota.

Date Posted

Evaluation of Intersection Collision Warning Systems in Minnesota

Summary Information

The Minnesota Department of Transportation (MnDOT) is investing in intersection collision warning systems (ICWS) based on early indications of effectiveness. The purpose of this report is to document effectiveness of these system. The objectives of this research were to (1) evaluate driver behavior at mainline and stop-controlled approaches for intersections with and without (ICWS) and (2) assess the traffic volume range and limits where the system is nearly continuously activated.


Video data were collected at five treatment and corresponding control intersections. Metrics, including stopping, gap size, glances, continuous activation using simulation, and conflicts, were used to compare changes in driver behavior. All conflicts were recorded for each intersection. Conflicts included near-crashes, evasive maneuvers, application of brakes or slowing, or changing lanes. Application of brakes or changing lanes was typically observed for mainline drivers, but any situation where evasive maneuvers were noted was coded as a near-crash.


The number of near-crashes was observed to decrease significantly at the treatment sites both 1 month (-8) and 12 months (-9) after ICWS installation. Conversely, the number of near-crashes increased from 22 events to 35 events at corresponding control sites during the 1-month period after ICWS installation. Near-crashes decreased again in the 12-month after period and ultimately showed no overall change from the before period.

The number of times drivers applied their brakes was another measure of conflict. The number of drivers who applied their brakes during the 1-month after period (22) at the treatment sites was similar to the number in the before period (22). More braking was noted during the 12-month after period (increase of 27 instances). The number of drivers applying their brakes increased significantly at the control sites between the 1-month and 12-month after periods.

Overall, near-crashes and other conflicts decreased at the treatment sites while they increased at the control sites. It is unknown why this was the case, but the team felt that these trends were not related to a spillover effect from the treatment sites.

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