This report documents the development of safety performance functions (SPFs) that include friction and macrotexture on a variety of roadway facility types and categories (i.e., segments, intersections, curves, and ramps). The main objectives of the report were: (1) the development of Crash Modification Factors (CMFs), or Crash Modification Functions (CMFx) that make it possible to evaluate the effect of pavement friction changes on safety performance, which can then inform the cost effectiveness of pavement friction improvements; and (2) the establishment of performance or investigatory thresholds for friction based on roadway type and category. The analysis confirmed a strong statistical association between pavement surface frictional properties (friction and macrotexture) and crash rates; lower crash rates were observed with higher friction and macrotexture. 

The findings from this report support road agency efforts toward the institutionalization of Pavement Friction Management, one of the FHWA Proven Safety Countermeasures. The results may be used by road agencies to inform safety analyses at both the system/network and site/project levels to evaluate the impact and cost-effectiveness of pavement friction enhancement strategies and treatments.