| description abstract | Safety performance functions (SPFs) are commonly used to correlate geometric, traffic, and environmental characteristics with total crashes, and to identify hotspots that have excessive overall crash frequencies. However, different crash types are associated with different vehicle maneuvers and therefore different risk factors. At signalized intersections, geometric design, signal control, traffic flow, and traffic crash occurrences vary across different approaches of a single intersection. This study developed approach-level SPFs using a full Bayesian method to assess the safety effects of specific risk factors for rear-end, left-turn, right-angle, and sideswipe crash types, and for total crashes. Based on these approach-level SPFs, a systematic method that efficiently integrated the procedures of hotspot identification and countermeasure development was proposed. The method can be used to identify high-risk intersection approaches with specific safety problems and can serve as a useful complement to general hotspot analyses that use expected crash totals. It was found that some variables, including the number of through lanes, median presence, and left-turn protection, could have contrary effects on the occurrence of certain crash types. The proposed method can provide insights to aid in the development of countermeasures aimed at reducing certain crash types and an improved ability to identify deficiencies related to geometric and traffic characteristics for each intersection approach. | |
