The objective of this effort is to develop safety performance functions (SPFs) for different types of facilities in North Carolina and illustrate how they can be used to improve the decision making process. The prediction models in Part C of the Highway Safety Manual were calibrated using data from North Carolina. SPFs were estimated for 9 crash types for 16 roadway types using statewide data from North Carolina – these SPFs just include AADT and can be used for network screening. In addition, SPFs for rural two lane roads were developed using AADT and other site characteristics including shoulder width/type and terrain. Using examples, this report outlines how the different SPFs can be used for network screening, project level analysis, and before-after evaluation using the empirical Bayes method. Finally, there is a discussion of how NCDOT can use the SPFs in the future by either calibrating the SPFs developed in this effort and/or develop SPFs using negative binomial regression. Along with the final report are Excel files that can be used by NCDOT to calibrate the SPFs in the future and to implement the HSM prediction methodology. (Author/publisher)
Abstract