Frequently Asked Questions
The Frequently Asked Questions (FAQs) are questions and answers about Compliance,
Safety, Accountability (CSA) that the Federal Motor Carrier Safety Administration
(FMCSA) compiled to assist the public. As questions come in through the website,
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Can you explain the research behind the Safety Measurement System (SMS) violation
severity weightings?
Answer
First, applicable safety-based violations of the Federal Motor Carrier Safety Regulations
and the Hazardous Materials Regulations were classified into the seven Behavior
Analysis and Safety Improvement Categories (BASICs). Next, within each BASIC, similar
violations were grouped together. For example, the Vehicle Maintenance BASIC has
tire and brake groupings, among others. Within each BASIC, the violation groups
were assigned severity weights that reflect the violation group's association with
crash occurrence and crash consequences. The stronger the relationship between a
violation group and crash risk, the higher its assigned weight.
The violation severity weights have been converted into a scale from 1 to 10, where
1 represents the lowest crash risk and 10 represents the highest crash risk relative
to the other violations in the BASIC. Since the weights reflect the relative importance
of each violation within each particular BASIC, they cannot be compared meaningfully
across the various BASICs. In other words, a rating of 5 in one BASIC is not equivalent
to a rating of 5 in another BASIC, but it does represent the midpoint between a
crash risk of 1 and 10 within the same BASIC. This data is summarized in Appendix
A of the
SMS Methodology and the
SMS Methodology document in Excel format.
These weights are based on a number of studies that quantify the associations between
violations and crash risk, as well as statistical analysis and input from enforcement
subject matter experts and feedback from the motor carrier industry. Subject matter
experts from FMCSA's field staff, including enforcement personnel and CSA development
team members, examined these severity weights during the Operational Model Test
and submitted recommendations to the agency to better associate crash risk with
the violations. These recommendations have been incorporated into the latest version
of the SMS Methodology.
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