5.4.4 Selecting CMFs

Special attention is necessary when selecting CMFs for use in safety analysis to make sure that the practitioner is selecting appropriate CMFs. The primary goal is to select a CMF that was developed under the same (or very similar) conditions as the location for which it is being applied. When selecting CMFs, consider the following characteristics:
  • Countermeasure type;
  • Crash type;
  • Crash severity;
  • Roadway or intersection type;
  • Area type (rural vs. urban);
  • AADT ranges;
  • Prior conditions; and
  • Similarity to locality where data is used
If multiple CMFs are available and appear to be similar or equally applicable, it is suggested that the following items related to the quality of the CMFs are reviewed to determine the best possible match:
  • Star rating;
  • Score details; and
  • Age of data or study
When selecting CMFs for use in analysis from the CMF Clearinghouse, the CMF IDs are recommended to be documented, and the CMF detail summary page can be provided. This information can be saved as a PDF and included as an appendix or attachment to the analysis documentation.
It is critical that sound engineering or professional judgment be used when selecting CMFs. Additional guidance on selecting CMFs is available in the following link:
Appendix F, Section 3 – External References (Reference 3)
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