Updated CMF Star Ratings

The CMF Clearinghouse transitioned to the CMF rating criteria developed as part of the NCHRP 17-72 project for the 2nd edition of the Highway Safety Manual on February 15, 2021. This flyer provides an overview of the legacy CMF Clearinghouse star rating criteria, as well as the NCHRP 17-72 criteria. This flyer provides details about what has changed as a result of this rating transition and how these changes might impact users.

This spreadsheet can be used to compare the legacy star ratings vs. the updated star ratings.

Two webinars were held on February 18, 2021 and February 23, 2021 to provide practitioners and researchers an opportunity to learn more about the rating system changes and how to navigate these changes on the CMF Clearinghouse website. If you missed these webinars, you can always watch the recording HERE.

The following video provides an overview of the CMF Clearinghouse rating transition and answers questions regarding what’s changing and what to expect as a result of this transition.

Below are a series of frequently asked questions.

Rating Procedure developed by NCHRP 17-72 for the 2nd Edition of Highway Safety Manual

As part of the ongoing NCHRP 17-72 project, a CMF rating system has been developed to identify CMFs for inclusion in the 2nd Edition of Highway Safety Manual. This rating system is much more rigorous and provides scores for various factors (there are multiples levels within factors and points for each level). The following table provides a summary of the factors used for the various study types:

Before/After and Cross-Sectional Studies

Meta-Analysis Studies

Meta-Regression Studies

Sample size

Methodology and data

Methodology and data

Study design and statistical methodology

Individual CMF quality

Individual CMF quality

Statistical significance

Appropriateness of combining

Appropriateness of developing a crash modification function

Statistical significance

Appropriateness of statistical analysis

The total score is calculated by adding the points for the different factors, with a maximum possible score is 150. The detailed rating criteria for each study type can be found here.

Will the CMF Clearinghouse maintain the star rating for each CMF?

The CMF ratings in the CMF Clearinghouse continue to be presented in the form of a 5-star scale, along with the total score calculated using the NCHRP 17-72 rating criteria. This provides CMF Clearinghouse users the detailed scores for the various factors (and levels within factors) to aid in better decision making. The traditional 5-star rating is determined based on the number of points a CMF earned using the rating system developed as part of NCHRP 17-72.

What Happens to the Star Ratings for CMFs currently in the CMF Clearinghouse?

Legacy Ratings for all the CMFs (prior to the rating system transition) have been converted to reflect the new rating criteria. We understand that DOTs and practitioners have been using the CMF Clearinghouse star ratings to inform their decision making. The transition to the NCHRP 17-72 rating criteria has lead to few instances where the star rating for current CMFs have changed (there are some higher rated CMFs that score low under the new rating criteria, as well as some lower rated CMFs that score high under the new rating criteria).

To minimize the impact of these changes, this spreadsheet is available to the CMF Clearinghouse users and can be used to compare the legacy star ratings vs. the updated star ratings for all the current CMFs (prior to the rating system transition).

CMFs added to the CMF Clearinghouse after the rating system transition would only be rated based on the new criteria.

Visit the CMF Clearinghouse for the most up to date information about the transition or contact Karen Scurry (karen.scurry@dot.gov) if you have specific questions regarding this rating system transition.