Calibration and Development of Safety Performance Functions for New Jersey
The predictive models provided by the Highway Safety Manual (HSM) are based on safety performance functions (SPFs), which are statistical regression models based on observed crash data from similar facility types that estimate the predicted average crash frequency for the base conditions. To make the SPFs better accommodate the local data, two strategies are usually undertaken: the first strategy is to calibrate SPFs provided in HSM so that the contents of HSM can be fully leveraged and the second strategy is to develop location-specific SPFs regardless of the predictive modeling framework in the HSM. The main objective of this talk was to summarize the NJDOT project titled “Calibration / Development of SPFs for New Jersey”. The aim of this project was both to calibrate and develop the SPFs provided in the HSM using New Jersey (NJ) data. The facility types considered in this research project included segments and intersections of rural two-lane two-way, rural multilane, and urban and suburban roads. Calibration and development of SPFs both required significant time, effort and resources, and detailed data from different sources. This talk also presented a detailed discussion of data needs and availability, data processing methods and approaches to gather the required data for calibration and development of SPFs. While presenting the results of the SPF calibration and development process, this talk also pointed to the importance of crash location information and its impact on analyses results.