Calibration of Safety Performance Functions for the Michigan Department of Transportation
More than 30,000 people die in traffic accidents each year in the United States. To reduce this number, the Moving Ahead for Progress in the 21st Century Act (MAP-21) requires states to implement a Highway Safety Improvement Program (HSIP). A state’s HSIP plan must emphasize using data to derive a strategic approach for improving highway safety. One tool available to states is safety performance functions (SPFs) listed in the Highway Safety Manual (HSM). SPFs can be used to evaluate the relative safety of design alternatives and to help states prioritize sites for roadway safety improvement. However, SPFs cannot account for every roadway characteristic; states must calibrate their SPFs based on their own crash data. This study is being conducted to calibrate SPFs for the Michigan Department of Transportation (MDOT) for urban trunk-line roads for four intersection types (3-leg/4-leg stop-control and 3-leg/4-leg signalized). Data is currently being collected on sample intersection characteristics for analysis using one of the methods outlined in HSM. Additionally, a procedure for updating these SPFs as crash patterns change is also being developed to ensure that these SPFs are practice ready. These findings will help MDOT implement targeted safety improvements across their transportation network.