Traffic conflict models and standards for signalized and unsignalized intersections

This paper describes the application of the traffic conflict technique to estimate the traffic safety at intersections. Using the data collected from 94 conflict surveys, traffic conflict frequency and severity standards for signalized and unsignalized intersections have been established. These standards allow for the relative comparison of the conflict risk at various intersections. An Intersection Conflict Index (ICI) measure was developed to summarize the conflict risk at intersections. The ICI provides an indication regarding the relative risk of being involved in a conflict at an intersection. In addition, regression analysis was used to develop predictive models which relate the number of traffic conflicts to traffic volume and accidents. The regression analysis results indicated that: (i) the average hourly conflict rate (AHC) and the average hourly severe conflict rate (AHC 4+) correlated reasonably well with traffic volume for both signalized and unsignalized intersections, (ii) strong relationships between accidents and conflicts were obtained for signalized intersections only. These research efforts are expected to further enhance the usefulness of the Traffic Conflict Technique as a tool to evaluate the safety of intersections.