Evaluation of Intersection Conflict Warning System: A Critical Gap Analysis

Rural intersections account for around 30% of crashes in rural areas and 6% of all fatal crashes. An Intersection Conflict Warning System (ICWS) is a unique solution to address rural intersection safety. ICWS are typically installed at the minor approaches to two-way stop-controlled intersections to reduce the number of fatalities. Studies indicate these systems result in lower intersection approach speeds, reduced conflicts, and improved driver-gap selection. However, some sites have experienced increases in the number of minor crashes. Although there are positive ICWS examples, their overall effectiveness is not well established. The objective of this research was to evaluate driving behavior at stop-controlled approaches with and without ICWS and to evaluate the spillover effect of ICWS on other adjacent control intersections where the treatment has not been applied. The study examined behavior at five intersections (treatment sites) in Minnesota where an ICWS was installed. For comparison, an additional five similar (control sites) were identified in proximity to each treatment intersection. Data were collected using a video camera array at three different time frames: before, one month, and 12 months after the installation of system. The data were analyzed using a critical gap approach. The analysis shows that the ICWS improved driver gap acceptance at the treatment sites, only at the 12-month period, and that there was no “spillover effect” at the adjacent control sites. When gap acceptance was further compared by type of stop, critical gap selection was shown to increase for drivers making both complete and rolling stops.