CMF Update, Summer 2014


The summer 2014 edition of CMF Update is the ninth edition of the Crash Modification Factors Clearinghouse e-newsletter. To subscribe, please visit http://www.cmfclearinghouse.org/newsletter_signup.cfm.

To view archived issues, please visit
http://www.cmfclearinghouse.org/newsletter.cfm.

New Clearinghouse features make searching more efficient

The CMF Clearinghouse is now more informative and easier to use, thanks to several recent updates:

Subcategories in search results: Search results are now not just grouped by category, but also by subcategory. For example, the category “Intersection traffic control” will show several drop down sub category options, including “turn prohibitions/permissions,” “traffic control visibility,” etc. Users can collapse and expand each subcategory to show the list of available countermeasures. This organizational change should allow users to more quickly locate the most appropriate countermeasure.

Comments within results table: Some CMFs have special conditions that a user needs to know about. For example, the CMF may only apply to special conditions, like motorcycle crashes during winter months. Previously, comments of this sort were provided only on the CMF details page. A column has now been added to show comments in the initial search results table, so that users can easily see that special comments have been made on a particular countermeasure.

Related CMFs and citations: Occasionally, study authors will publish several articles or papers from a single data set. The Clearinghouse now recognizes this relationship by identifying related studies on the “Study Details” page, enabling users to see more clearly the connections between studies.

Finally, do you use Safety Performance Functions (SPF) to predict crash frequency based on site conditions? Be sure to check out the Clearinghouse’s new SPF Resources section. This section includes guidebooks on developing SPFs and calibration factors, as well as how to choose between using SPFs from the Highway Safety Manual versus developing jurisdiction-specific SPFs.

Please enjoy these new CMF Clearinghouse features! For questions about the updates, or to suggest future changes, contact Karen Scurry, FHWA Office of Safety Programs, at karen.scurry@dot.gov.


Featured CMFs

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

Install raised pavement markers with restriping (center and edgelines)

Crash Modification Factor (CMF) Value: 0.69

Star Quality Rating: 4 stars

Convert an open median to a directional median

Crash Modification Factor (CMF) Value: 0.77

Star Quality Rating: 4 stars

Install cable median barrier
Crash Modification Factor (CMF) Value: 0.35

Star Quality Rating: 3 stars


Featured resource: Tips for building high-quality CMFs

Are you considering developing a CMF from your research? By doing so, you provide valuable data for use in safety, design and analysis decisions. “Better CMFS, safer roadways: Tips for building high-quality CMFS,” is a two-page tip sheet that provides an overview on how to develop reliable CMFs, and answers questions such as, “What does a quality CMF study look like?” and “Why is documentation important?” It stresses the importance of accuracy, precision and general applicability of study results in creating CMFs. For example, common characteristics of high-quality CMFS include: statistically rigorous study design, large and diverse sample size, small standard of error, control of potential biases and diverse geographic data. The tip sheet is available in the resources section of the CMF Clearinghouse website.


Featured FAQ: How do the Clearinghouse crash severity terms relate to the KABCO injury scale?

We initially planned for the Clearinghouse to use a standard KABCO scale. However, we found that, much like other study details in the Clearinghouse database, authors can and do report the details of their CMFs in many different ways. Authors have reported crash severity by KABCO, by maximum abbreviated injury scale (MAIS), or simply by referring to “serious injury” and “minor injury.” Thus, the Clearinghouse uses the lowest common denominator. There is no one-to-one comparison with KABCO, but the best comparison is that “Fatal” is always equivalent to K, “Serious Injury” would generally be A and B injuries, and “Minor Injury” would generally be C injuries.


Submit a study

The CMF Clearinghouse welcomes CMF study submissions to be included in its searchable database. Please use the provided form at http://cmfclearinghouse.org/pubsubmit.cfm 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.

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.