Development of Expected Conflict Value Tables for Unsignalized Three-Legged Intersections

A high percentage of highway crashes in the United States occur at intersections. These crashes result in property damage, lost productivity, injury, and even death. Identifying intersections associated with high crash rates is very important to minimize future crashes. Identifying the high-risk intersections before crashes occur is a challenge that every traffic/safety analyst faces. Traffic conflict technique is a solution to this problem. Extensive research efforts have been made to estimate mean and abnormal traffic conflict counts at four-legged intersections with varying lane and approach volume conditions. However, similar efforts on unsignalized three-legged intersections have been focused only on two-lane highways. Therefore, a thorough analysis of conflicts at unsignalized three-legged intersections with various lane combinations was necessary. The current study is part of a comprehensive research attempt to develop expected conflict value tables that can be easily used for different intersection configurations. The most common unsignalized threelegged intersection types (total of three) were identified and categorized based on through lanes of the intersection. During the summer of 1995, 12 different traffic conflict types were surveyed from 38 intersections randomly sampled from a five-county area in west-central Florida. Combining a recent 3-year crash history and the collected conflict data of the sampled intersections, new and easy-to-use tables were developed for Florida-based unsignalized three-legged intersections. The tables provide mean, variance, and 90th and 95th percentile conflict rates. These simplified tables can be used to estimate the expected number of crashes, relative safety effectiveness, and operational problems at intersections.