Association Between Access Management and Traffic Safety: Median Classification and Spatial Effect

This study examines the relationship between safety and access management with respect to median-related crashes. Using data from 2,500 unsignalized intersections in Florida, six possible median types that could exist in the vicinity of unsignalized intersections were identified. The six median types were: open, closed, directional, two-way left turn lane, undivided and mixed. The authors identify various median-related crash patterns that could exist at each of the median types related to unsignalized intersections/access points. Median-related crashes were differentiated from intersection-related crashes to improve understanding of the relationship between median-related crash occurrences and geometric and traffic features. The results showed that open medians were the most dangerous median type and closed medians were the safest. Rear-end and angle crashes were the most dominant types of crashes at all median types. Important variables that affected median-related crashes included median width, speed limit on the major road, logarithm of annual average daily traffic, logarithm of upstream and downstream distances to the nearest signalized intersection, and crash pattern. Based on these findings, safety countermeasures for improving access management are recommended. These countermeasures included closing median openings in the vicinity of most unsignalized intersections whenever possible, adequately spacing signalized intersections away from driveways and unsignalized intersections with restricted medians, and avoiding two-way left turn lanes in the vicinity of four-legged intersections.