# Potential SMS Improvements for MCSAC CSA Subcommittee April

Potential SMS Improvements for MCSAC CSA Subcommittee April 2014 Agenda Potential SMS Methodology Improvements Low/Medium/High (L/M/H) Severity Weighting Dynamic Safety Event Groups (SEG) 2 Violation Severity Weight Purpose One of the goals of the CSMS is to identify habitual safety problems. Severity weights help tune CSMS by differentiating varying degrees of crash risk associated with specific violations. The violations and their associated severity weights are calculated across multiple inspections to identify

systemic safety issues. 3 Violation Severity Weights Background General Approach: Cover all safety-based roadside inspection violations in a systematic manner. Develop weights based on empirical analysis to the extent possible. Supplement results with expert judgment. Because each BASIC is calculated independently in the CSMS, develop the violation severity weights relative to the crash risk associated with only the violations within the same BASIC. Results: Assigned severity weight from 1 to 10 scale (where 1 represents lowest crash risk, 10 represents the highest within the BASIC) to every safety-based violation. 4

Severity Weight Example Analysis Driver Regression Model Example: Unsafe Driving BASIC Violation Group Regression Coefficients Statistically Significant Reckless Driving 1.94 Yes

Dangerous Driving 1.17 Yes Speeding Related 1.11 Yes Other Driver Violations 1.11 Yes HM Related

1.00 No Statistical coefficients were used to generate initial violation severity weights from 1 to 10. 5 Lessons Learned Easily observable violations (e.g., tires, lights) are weighted more in some instances than violations that would intuitively be more likely to cause a crash. Approach based on statistical and observed Relationship of violations to crashes. Relationship doesnt necessarily equate to causation. The level of precision of the severity weights is not a

major factor in identifying carriers with safety problems in the CSMS. Carriers with safety problems simply have more violations. 6 Problem Assigning 1-10 severity weight implies a level of safety risk precision (Is a severity rate violation of 6 more risky than a 4?) Stakeholder focus on individual violations (such as how did a particular headlight go out) instead of importance of preventing patterns of violations (Drivers conducting pre-trip, having solid maintenance programs, etc.) 7 Potential Solution: Simplified Severity Low, Medium, High

Calibrate to numerical weights associated with each severity classification. Examine driver-based model that links violation rates of drivers to crash involvement MCSAC recommendations SMS Effectiveness test results Recalibrate cap on max total severity weight from an inspection Consider how to treat OOS conditions. Example: Low = 1, Medium = 2, High = 3 OOS = +1 8

Agenda Potential SMS Methodology Improvements Low/Medium/High (L/M/H) Severity Weighting Dynamic Safety Event Groups (SEGs) 9 Purpose of Safety Event Groups (SEG) Source: GAO 2014 10 SEG Background Most BASICs currently have 5 SEGs. Example: HOS Compliance BASIC: SEG Number of Relevant Inspections

1 2 3 4 5 5-10 11-20 21-100 101-500 501+ 11 Explaining SEGs, Percentiles and Measures 65% 2.39 5-10 insp

11-20 insp 65% 1.70 21-100 insp 65% 1.39 101-500 insp 500+ insp Safety Event Group 65% 1.08 65%

0.54 Measure Range Percentile Associated Measure 12 Problem When moving from one SEG to another, a carrier can experience a dramatic percentile change (e.g. +/-15%) Changing the boundaries or sizes of the groups does not fix the issue Having more groups helps, but there are always jumps at the boundaries More drastic change is needed 13

Explaining SEGs, Percentiles and Measures 65% 2.39 5-10 insp 11-20 insp 65% 1.70 76% 2.25 1. Carrier has 10 inspection with a measure of 2.39 / 65% 2. Gets a new clean inspection slightly lower measure 2.25 3. Moves to 11-20 inspection SEG 4. Receives a higher percentile of 76

14 Potential Solution: Adjustments to SEGs Move from 5-tiered grouping to a dynamic or tailored SEG for each carrier based on: A carriers exact number of safety events (e.g. inspections), and Other carriers with the same or similar number of safety events 15 Dynamic SEG Example # of Safety Events of Carrier 5 inspections Current SEGs

Dynamic SEG 5-10 4-6 inspections 6 5-10 5-7 7 5-10 6-8 8

5-10 7-9 9 5-10 7-11 10 5-10 8-12 11

11-20 9-13 12 11-20 9-14 16 Expected Effect of Adjustments to SEGs Allows for carrier BASIC measures to be compared with the other carriers with same or closest number of events Eliminates current problem of large jumps in percentiles when carrier transitions from one SEG to the next

Still focus CSA efforts on carriers with the worst compliance/safety across all sizes 17

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