Safety Performance Functions (SPFs) in the Highway Safety Manual (HSM) were developed using historic crash data collected in different states. Because local state or geographic conditions vary, 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.NJDOT Research
The main objective of this research project is to (1) calibrate the SPFs provided in the HSM using New Jersey (NJ) data and (2) develop new NJ-specific SPFs as appropriate. The facility types considered for this research project include segments and intersections of rural two-lane two-way, rural multilane, and urban and suburban roads. The following tasks were completed to achieve the main project objective:
◦ Conducted an in-depth review of the relevant studies in the literature
◦ Identified the key sources of data required for calibration and development of SPFs. These include roadway characteristics data, traffic volume data, and crash data.
◦ Developed a computer code to read and process the compiled database to (a) filter out inconsistent data entries, (b) identify facility types, (c) execute roadway segmentation process, (d) assign crash statistics for each facility, and (e) generate a complete database for each facility type to be used in calibration and/or development of SPFs.
◦ Provided recommendations to improve data collection and recording practices that would facilitate easier data extraction required for the SPF calibration/development process.
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