CMFs are located on the CMF Clearinghouse website, which is a central, web-based repository of CMFs. This website is a searchable database maintained by FHWA with the intent of serving three roles related to the transportation safety field: to educate CMF users, house CMF data for use, and facilitate continued CMF research. The CMF Clearinghouse website includes search features for CMFs applicable to the various countermeasures under consideration. A link to the CMF Clearinghouse is available in

Appendix F, Section 3 – External References (Reference 2)

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All CMFs in the Clearinghouse are evaluated and rated using the defined star rating system. CMFs are given a star rating from one to five stars. The star rating indicates the reliability and quality of a CMF, with five stars being the most reliable. The star rating system considers various factors from the study research that produced the CMF. These factors include data used, study design, study methodology, sample size, statistical significance, and location(s) where the data was collected. An updated star rating system was developed and implemented in February 2021 as part of the NCHRP) 17-72 project. As a result, many CMFs received a new star rating based on the updated evaluation criteria. CMF summary reports printed prior to February 2021 may contain star ratings that differ from their current star rating. Additional information about the star rating system’s evaluation criteria and the changes to the evaluation criteria are on the CMF Clearinghouse website.

Whenever possible, only CMFs with a star rating of three or higher may be used in analysis. If the best available CMF has a star rating lower than three, it can only be used if accepted by the TxDOT project manager assigned to approve the completed analysis. A CMF’s ID number and star rating is suggested to be documented if used for safety analysis.