• August 12th, 2020

Practitioners use Crash Modification Factors/Functions (CMFs) to calculate the number of crashes expected once a
countermeasure has been implemented. When evaluating design alternatives, CMFs can be used in conjunction with safety performance functions (SPFs) to derive crash predictions. The Federal Highway Administration (FHWA) maintains the CMF Clearinghouse as a repository for CMFs. Contributions are submitted by researchers across the U.S., Canada, and throughout the world. Typically, multiple CMFs are associated with a single countermeasure. Some CMFs only apply to specific facility or crash types. Furthermore, CMF quality varies, and some only apply to specific facility and/or crash types, regions, or times. Using the Clearinghouse to identify an appropriate CMF for a given situation demands considerable time and significant expertise. This report describes the development and implementation of a spreadsheet-based tool that Kentucky Transportation Cabinet staff and the agency’s design consultants can use to select CMFs most appropriate for the state’s highways and conditions. Guidance instructs users on use of the tool. A web-based form was also developed, which must be filled out and submitted to KYTC’s CMF committee when a CMF is planned for use on a project.

Read the full study here.