Crash Modification Factors in Practice - Introduction to Safety Performance Functions

2013PDFBriefFHWA-SA-13-016Crash modification factorsTraffic safetyPerformance measurementUnited StatesUnited States. Federal Highway Administration. Office of SafetyUnited States. Federal Highway Administration. Office of SafetyScurry, KarenFederal Highway AdministrationA safety performance function (SPF) is an equation used to predict the average number of crashes per year at a location as a function of exposure and, in some cases, roadway or intersection characteristics (e.g., number of lanes, traffic control, or median type). For highway segments, exposure is represented by the segment length and annual average daily traffic (AADT) associated with the study section as shown by the sample SPF in Equation 1.93