CMF Update, Winter 2014

The winter 2014 edition of CMF Update is the 10th edition of the Crash Modification Factors Clearinghouse e-newsletter. To subscribe, please visit

To view archived issues, please visit

New FWHA CMF Clearinghouse webinar -- Register today!

Applying (or misapplying!) CMFs: The ins and outs of estimating crash reductions
Thursday, Dec. 11
2:00-3:30 Eastern
Register here

Join transportation engineers, designers and planners from across the country to learn about recent updates to the Federal Highway Administration’s (FHWA) CMF Clearinghouse, and how to better apply -- and how to avoid misapplying -- crash modification factors!

Daniel Carter, researcher at the UNC Highway Safety Research Center and manager of the CMF Clearinghouse, will begin this FREE webinar with a brief overview of new Clearinghouse features, with a focus on how to select the CMF most appropriate to a specific scenario.

Frank Gross, highway safety engineer at Vanasse Hangen Brustlin, Inc., will discuss common errors in applying CMFs and how misapplication of CMFs can lead to overestimating or underestimating the potential benefits of a countermeasure.

Finally, John Milton and Jennene Ring from Washington State DOT will share how they developed a CMF “short list” for their state and will present an example or two of how they use CMFs to evaluate and prioritize projects.

Do you have questions about applying CMFs? Be sure to stay for the end of the session for a brief Q&A session!

Continuing education: Attendees will be eligible to receive a certificate of completion for 1.5 hours that can be applied toward Professional Development Hours (PDH) credit, per State requirements. This event will also be submitted for American Institute of Certified Planners (AICP) credits.

Questions? Contact Daniel Carter at for more information.

Featured CMFs

The CMF Clearinghouse is continually updated with new CMFs. Below are CMFs recently added to the Clearinghouse database.

Install edgeline pavement markings on narrow, rural, two-lane roads

Crash Modification Factor (CMF) Value: 0.85

Star Quality Rating: 3 stars

Active work with no lane closure (compared to no work zone)

Crash Modification Factor (CMF) Value: 1.168

Star Quality Rating: 3 stars

Install J-turn intersection
Crash Modification Factor (CMF) Value: 0.652

Star Quality Rating: 4 stars

Featured resource: Application of Crash Modification Factors course

This course, presented by FHWA’s National Highway Institute, focuses on the application of CMFs to select countermeasures. It covers the project development cycle (starting from network screening and site selection for safety review), diagnostics of safety concerns, cost-benefit evaluation, and countermeasure selection. Upon completion of the course, participants will be able to explain how CMFs are used to estimate the safety effects of highway improvements and apply CMFs to compare and select highway safety improvements.

This course combines a web-conference and a self-paced lesson that aids in application to your current projects. You will need access to both a telephone and Internet connection to participate in the live web session on Feb. 18, 2015 at 1-3 p.m. EST. For additional details and pricing information, see the online course description.

Featured FAQ: How is the star quality rating different from the notations (bold, italics, etc.) in the Highway Safety Manual?

The star rating and the Highway Safety Manual (HSM) notation are similar but different. Both indicate the same thing, which is a confidence in the CMF based on the quality of the study that produced it. In a rough sense, higher star ratings correspond to a bold face HSM notation and mid-range star ratings correspond to italics and asterisk HSM notations, but there is not a one-to-one comparison laid out between the two systems. The differences exist in the way the CMFs are reviewed to determine their quality.

The HSM review process applies an adjustment factor to the standard error from the study, and then assigns the bold and italic notations based on ranges of the adjusted standard error. The standard error is adjusted based mainly on the quality of the study design. The HSM assigns asterisk (*) or caret (^) notations based on the confidence interval of the CMF, which indicates how accurate the CMF estimate is.

The CMF Clearinghouse review process rates the CMF according to five categories — study design, sample size, standard error, potential bias, and data source — and judges the CMF according to its performance in each category. It assigns a star rating based on the cumulative performance in the five categories. It differs from the HSM process in that it does not attempt to adjust the standard error as the HSM does, and it more explicitly considers criteria such as data source, which examines whether a study used data from just one locality or from multiple locations across the state or nation.

Submit a study

The CMF Clearinghouse welcomes CMF study submissions to be included in its searchable database. Please use the provided form at to submit your study. Be sure to search before submitting a new CMF as it may already be listed. You may either submit a link to a resource already existing on the web (preferred) or upload your own file. Submissions might include published research studies that are not presented in the Clearinghouse, or state-specific CMFs that were developed as part of the Highway Safety Improvement Program.