Crash modification factors (CMFs) and functions are developed from historic crash data and help safety professionals estimate the expected safety impacts of specific roadway treatments. There has been a significant amount of research to develop CMFs for common safety strategies and many are included in the AASHTO Highway Safety Manual (HSM) and Federal Highway Administration (FHWA) CMF Clearinghouse. However, there are many instances in which developing reliable CMFs with conventional crash-based evaluations may not be practical or possible. For example, using crash data to evaluate innovative intersection designs or new traffic control strategies requires multiple years of data collection to accumulate a sufficient number of installations and crash history. Additionally, countermeasures that improve safety for crash types such as bicycle, pedestrian or other vulnerable road user crashes, are often lacking in quality CMFs because crash data is limited or not available. Research is needed to develop and apply new methods for developing CMFs or other quantifiable measures of safety for these cases, such as conflicts, speed changes, and lane deviations.
The objective of this project was to develop a procedural guide for using alternative measures of safety in the absence of crash data for developing crash modification factors and functions and other quantifiable measures in the absence of crash data. The new measures were to be evaluated against established crash-based measures. In addition, it was expected that the new measures of safety developed would span a range of site conditions, crash types and severity. The procedural guide is to support informed decision making during project planning, project development, and other road safety management activities and include several use case studies.
STATUS: Research is complete. Final report and associated deliverables are available at https://www.trb.org/Publications/Blurbs.aspx?fields=PublicationType|NCHRPReport.