The paper describes the development of new safety performance functions for interchanges, ramps and ramp terminals for Ontario freeways, using negative binomial regression modelling that relates collision frequency to traffic volumes and basic entity characteristics. Also presented is the application of these safety performance functions for network screening using two varieties of the potential for safety improvement (PSI) index method. A third method, which is based on an index of a high proportion of a specific collision type, is applied to ramp terminals by way of illustration to identify those sites with high proportions of specific collision types. This work has been developed as part of the continuing efforts of the Ministry of Transportation Ontario to establish a state-of-the-art knowledge base on the interaction of human factors, highway design and highway safety that can be put into practical use. For the covering abstract of the conference see ITRD number E211521.
Abstract