How to Develop and Use CMFs

CMFs in Practice
The CMFs in Practice Series includes five separate guides that identify opportunities to consider and quantify safety in specific activities, including roadway safety management processes, road safety audits, design decisions and exceptions, development and analysis of alternatives and value engineering. The series also includes reference documents that provide background information on crash modification factors and safety performance functions.

Recommended Protocols for Developing Crash Modification Factors
The CMF Protocols provide guidance for the development and documentation of research studies that develop CMFs. The major goal of these protocols is to describe what pieces of the research study should be documented by the study authors and how various potential biases should be addressed.

A Guide to Developing Quality Crash Modification Factors
The purpose of this guide is to provide direction to agencies interested in developing crash modification factors (CMFs). Specifically, this guide discusses the process for selecting an appropriate evaluation methodology and the many issues and data considerations related to various methodologies.

Investigation of Existing and Alternative Methods for Combining Multiple CMFs
This paper brings to light several issues associated with the application of multiple CMFs and provide guidance on how to estimate the combined treatment effect when multiple treatments are installed at a given location. The paper presents several existing methods for combining multiple CMFs and discusses the associated issues. Next, several ideas are explored for overcoming the identified issues. Finally, the methods are applied and compared to existing CMFs for multiple treatments in an attempt to validate the new procedures.

Better CMFs, safer roadways: Tips for building high-quality CMFs
This two-page flyer provides a basic overview on how to develop high-quality CMFs, with information on questions such as, “What does a quality CMF study look like?” and “Why is documentation important?”

The information contained in the Crash Modification Factors (CMF) Clearinghouse is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in the CMF Clearinghouse. The information contained in the CMF Clearinghouse does not constitute a standard, specification, or regulation, nor is it a substitute for sound engineering judgment.