CMF Clearinghouse Case Study
Let’s consider a scenario with an existing two-lane highway segment experiencing high crash frequencies. We want to evaluate the effects of installing rumble strips and there are two design options:
(a) Install centerline rumble strips
(b) Install shoulder rumble strips
![Centerline Rumble Strips](https://mctranswordpresssa.blob.core.windows.net/uploads/2024/11/Centerline-Rumble-Strips.webp)
Install centerline rumble strips
For the first alternative scenario (centerline rumble strips), the analysis process is straightforward as this treatment is, by default, included in the Highway Safety Manual Part C methods. The user checks the “Centerline Rumble Strips” box in HSS, and a CMF of 0.94 (6% reduction in crashes) is applied according to HSM principles:
![Centerline Rumble Strips and CMF option in HSS](https://mctranswordpresssa.blob.core.windows.net/uploads/2024/11/Centerline-Rumble-Strips-and-CMF-option-in-HSS.png)
Install shoulder rumble strips
The second alternative scenario (shoulder rumble strips) is not a treatment included in the HSM Part C methods. Therefore, a CMF from the Clearinghouse will be used (ID #1195):
![CMF from the Clearinghouse](https://mctranswordpresssa.blob.core.windows.net/uploads/2024/11/CMF-from-the-Clearinghouse.png)
To apply this CMF using HSS 2025, simply add it to the segment analysis using the new “User-Defined CMFs” input table. For this example, this particular CMF is expected to reduce crashes of all severities by a proportion of 13%:
![Using CMF in HSS 2025](https://mctranswordpresssa.blob.core.windows.net/uploads/2024/11/Using-CMF-in-HSS-2025.png)