This investigation compares collisions at intersections with permissive-and-exclusive left-turn arrow operation. Three (3) intersections included dual-left-turn lanes in only one direction and three (3) intersections included single-left-turn lanes in both directions. Seventeen years of data were analyzed. The analyses of the collision experience in the City of Scottsdale, Arizona, USA reveals that there is a statistical significant difference in the percentage of collisions involving left-turning vehicles and the left-turn collision rates between permissive-and-exclusive left-turn arrows with dual-left-turn lanes in only one direction, and permissive-and-exclusive left-turn arrows with single-left-turn lanes in both directions. For both collision measures, the intersections with permissive-and-exclusive left-turn arrows with dual-left-turn lanes in only one direction experienced more collisions than the intersections with permissive-and-exclusive left-turn arrows with single-left-turn lanes in both directions. Of greatest importance are left-turn-head-on collisions - the most critical types of left-turn collisions. The mean left-turn-head-on collision rate at intersections with permissive-and-exclusive left-turn arrows with dual left-turn lanes in only one direction was discovered to be approximately three times the mean collision rate at intersections with permissive-and-exclusive left-turn arrows with single left-turn lanes in both directions.
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