SAFETY PERFORMANCE EVALUATION OF INTERSECTION TRAFFIC AND SAFETY ASSETS: METHODOLOGY AND APPLICATION
Due to the large number of intersections in transportation networks, the complexity of potential conflicting traffic movements, and the wide variety of geometric and operational features at these locations, the safety at roadway intersections is of significant interest. A variety of crash types occur at intersections every year including head-on, sideswipe-same, sideswipe-opposite, fixed object, rear-end, fixed object, turning, and angle crashes. While a total of crashes at intersections may not reveal a site deficiency, prevalence of a specific crash type may reveal otherwise undetected deficiencies. To analyze the interrelation between deficiencies and crashes, a risk-based methodology is for computing a safety index that assesses impacts of safety hardware conditions on vehicle crashes. It incorporates a disaggregated risk-based approach for computing the safety index that assesses the impacts of intersection safety hardware such as signs, signals, lighting, and pavement markings on vehicle crashes. With safety indices estimated before and after implementation of an intersection safety hardware project, the annual potential for safety improvements (PSI) could be computed. Potential hazards, which are assessed by measuring risk in relation to road features that may lead to future crashes, so that remedial treatments may be implemented before crashes happen. A computational study is conducted for methodology application and validation to remove or change the features which contributed to those past crashes using 7-year data on 93 signalized intersections which have been equipped with red-light running enforcement devices in Chicago, Illinois. The results are compared with Empirical xii Bayesian Estimates via the statistical tests in order to validate the proposed methodology. Finally, it discusses future directions for continuing refinements of the proposed riskbased methodology. The proposed methodology could be adopted by state and large-scale local transportation agencies for intersection safety hardware project evaluation.