The Winter 2020 edition of CMF Update is the 22nd edition of the CMF 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.
In this issue:
The CMF Clearinghouse will transition to the CMF rating criteria developed as part of the NCHRP 17-72 project for the Update of CMFs for the Highway Safety Manual on or about February 15, 2021. The rating system developed as part of the NCHRP 17-72 project is more rigorous than the existing CMF Clearinghouse rating criteria and provides scores for different factors including sample size, study design, methodology, and statistical significance. There are multiple levels and associated points for each factor. The total score is calculated by adding the points, with a maximum possible score of 150.
The CMF Clearinghouse will continue to present CMF rating on a 5-Star scale, along with the total score calculated using the NCHRP 17-72 rating criteria. The crosswalk from the 150-point NCHRP 17-72 rating scale to the traditional CMF Clearinghouse Star rating scale is shown in the following table.
|NCHRP 17-72 Rating Score||Star Rating|
Under the new rating criteria, a CMF must score a minimum of 75 points (i.e., 50% of the total points) to receive a 3-Star rating. There will be movement between the star ratings with some CMFs being rated differently from their current ratings in the CMF Clearinghouse. These movements in star ratings can be attributed to various factors with the most prevalent ones being non-reporting of the number of crashes and number of miles/sites used for CMF development.
To minimize the impact of rating changes to the current CMFs, the CMF Clearinghouse will provide users with a spreadsheet consisting of both the old and new star ratings for the CMFs currently in the CMF Clearinghouse. However, CMFs added to the CMF Clearinghouse after the rating transition would only show the ratings based on the new criteria.
This FLYER provides details about what is going to change as a result of this rating transition, how this change might impact users and what users can do to prepare for the transition. Visit the CMF Clearinghouse for the most up-to-date information about the transition.
If you missed the CMF Clearinghouse annual webinar in December, you can always watch the recording on the CMF Clearinghouse website. Watch the December webinar, Understanding the Upcoming CMF Rating Transition and Exploring Real-World Applications of CMFs, to learn about the upcoming CMF Clearinghouse rating transition and how Caltrans and TxDOT are using CMFs in traffic impact studies and prioritizing HSIP projects, respectively.
Taha Saleem, manager of the CMF Clearinghouse, discussed the CMF Clearinghouse transition to the CMF rating criteria developed as part of the NCHRP 17-72 project for the Update of CMFs for the Highway Safety Manual and what is going to change. Troy Bucko, Caltrans, discussed how Caltrans is Incorporating Data Driven Safety Analysis in Traffic Impact Studies (and how they use CMFs from the CMF Clearinghouse in this process). Srinivas Geedipally, Texas A&M Transportation Institute (TTI), discussed the process used by TTI to assist TxDOT in the review and development of the CMFs used for HSIP projects.
In addition, do you ever feel like there's so much information on the Clearinghouse that you have trouble finding exactly what you need? Karen Scurry presented an overview of CMFs and the CMF Clearinghouse and demonstrated how to make use of the features of the CMF Clearinghouse to sort through hundreds of countermeasures and CMFs to find the most appropriate CMF for your situation.
Watch the recorded webinar HERE.
Traditional crash and roadway analysis methods mostly rely on subjective or limited quantitative measures of safety performance. This dependence makes it challenging to calculate safety impacts alongside other criteria when planning projects. Data-Driven Safety Analysis (DDSA) employs newer, evidence-based models that provide State and local agencies with the means to quantify safety impacts similar to the way they do other impacts such as environmental effects, traffic operations, and pavement condition. DDSA provides reliable estimates of an existing or proposed roadway’s current and future safety performance and helps agencies make more informed decisions, better target investments, and reduce crashes occurring on their roadways.
FHWA developed a series of How-To Guides for incorporating DDSA in Traffic Impact Analysis, Road Diets, and Intersection Analyses Through the Use of Intersection Control Evaluations. These guides are available on the FHWA DDSA webpage.
Safety performance functions (SPFs) are one of the fundamental building blocks of the predictive methods in the Highway Safety Manual (HSM). One step in implementing the HSM is calibration of the HSM-provided SPFs or development of jurisdiction-specific SPFs. Many states have already completed this step. The State SPF Calibration Efforts Summary spreadsheet available on the CMF Clearinghouse website was updated in November 2020 and summarizes the results from States that have published and posted their SPF calibration factors and/or state-developed SPFs.
The CMF Clearinghouse website also provides a comprehensive list of State Selected CMFs (updated in December 2020). Generally, the states compiled these lists so that there would be consistency in CMF use across their state. These CMFs were identified from the CMF Clearinghouse as well as other resources.
If your state has developed or updated SPFs, SPF calibration factors or state selected CMF lists and you do not see your state mentioned in the lists on the CMF Clearinghouse, please contact Karen Scurry at firstname.lastname@example.org to have them featured on the CMF Clearinghouse.
Implement Adaptive Traffic Signal Control
Crash Modification Factor (CMF) Value: 0.948 (for all intersection crashes)
Star Quality Rating:
Install a Pedestrian Hybrid Beacon
Crash Modification Factor (CMF) Value: 0.818 (for all crashes)
Star Quality Rating:
Convert Continuous Green T-intersections to Conventional T-Intersections
Crash Modification Factor (CMF) Value: 0.665 (for all crashes)
Star Quality Rating:
The CMF Clearinghouse welcomes CMF study submissions to be included in its searchable database. If you wish to submit your CMF study, please email Karen Scurry at email@example.com. Be sure to search the Clearinghouse before submitting a new CMF as we may already have it listed. You may either send 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.