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Evaluation of the Conversion from Two-Way Stop Sign Control to All-Way Stop Sign Control at 53 Locations in North Carolina

Due to the perceived safety benefits, relative low cost, and ease of implementation of all-way stop control, there is growing interest in the conversion of intersections from two-way to all-way stop control in North Carolina. However, there are few current, up-to-date studies quantifying their safety benefits, especially for higher speed rural locations or locations equipped with flashing beacons. The purpose of this project was to develop crash reduction factors for the conversion from two-way to all-way stop control at a diverse group of intersections that reflect North Carolina conditions and decision making. Other places with similar conditions might benefit from the findings as well. A total of 53 treatment sites located in urban, suburban, and rural areas were chosen for analysis in this project. The treatment locations were divided into three groups based upon presence of an overhead and/or sign mounted flashing beacon. Group 1 consisted of 33 intersections without flashing beacons; Group 2 consisted of 8 intersections with flashing beacons in the before and after period; and Group 3 consisted of 8 intersections where the flashing beacon was installed with the all-way stop control. The results show a substantial decrease in total, injury, and frontal-impact crashes in the after period when analyzing all locations and Groups 1, 2, and 3. The recommended crash reduction factors for conversion from two-way to all-way stop control are the factors calculated by the empirical Bayes method with consideration for traffic increase. The recommended crash reduction factors from the overall group are a 68% reduction in total crashes, a 77% reduction in injury crashes, a 75% reduction in frontal-impact crashes, and a 15% reduction in “ran-stop-sign” crashes.