Methodology for Determining Motorcycle Operator Crash Risk and Alcohol Impairment. Vol. 1, Synthesis Report on Alternative Approaches with Priorities for Research

Voas, Robert B.; McKnight, A. James; Thom, David R.; Smith, Terry A.; Hurt, Hugh H.; Waller, Patricia F.; Zellner, John W. · 2007 · ROSA P / United States. National Highway Traffic Safety Administration

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Summary

This report, sponsored by the National Highway Traffic Safety Administration (NHTSA), addresses the critical gap in understanding the relationship between blood alcohol concentration (BAC) and crash risk for motorcycle operators. While the correlation between alcohol impairment and automobile crash risk is well-established, data regarding motorcycle operation is insufficient due to the unique demands of balance, coordination, and vulnerability inherent to riding. The study was motivated by rising motorcyclist fatalities and the high prevalence of alcohol involvement in fatal crashes, where 27% of motorcycle operators had a BAC of .08 g/dL or higher in 2004, exceeding rates for other vehicle types. The primary objective was to evaluate alternative methodological approaches for determining relative crash risk and impairment levels to guide future research priorities. The methodology involved a comprehensive literature review of 143 reports and websites, followed by a workshop with an expert panel of specialists in motorcycle safety, alcohol research, and survey methods. The panel assessed various data collection strategies, categorizing them by scientific validity and estimated cost. Methods examined included laboratory-based simulation studies, closed-course riding tests, contemporary case-control studies, cohort studies, emergency department data collection, self-report surveys, and analyses of archival crash records (such as the Fatality Analysis Reporting System). The panel evaluated each approach based on advantages, disadvantages, feasibility, and the ability to provide both crash data and population-at-risk exposure data. The findings prioritized methodologies based on a matrix of cost and scientific validity. The highest priority recommendations were Simulation and Induced Exposure studies within the lowest cost category (under $250,000), and Contemporary Case Control studies within the highest cost category (over $500,000). Simulation studies allow for controlled measurement of impairment at specific BAC levels, while Induced Exposure studies utilize existing archival data to compare at-fault and non-at-fault riders. Contemporary Case Control studies were deemed highly valid for determining relative risk by comparing crash-involved riders with non-crash-involved riders at similar locations and times. Conversely, Cohort Studies were assigned the lowest priority despite high scientific validity due to prohibitive costs and time requirements. Survey studies and Geo-General comparison data were also rated lower priority due to issues with data accuracy and representativeness. The significance of this report lies in its structured framework for future research on motorcycle safety. By identifying the most feasible and scientifically robust methods, the study provides a roadmap for generating the missing data on alcohol impairment in motorcyclists. The prioritization allows researchers to select appropriate methodologies based on available funding, ensuring that future studies can effectively address questions regarding vulnerability at different BAC levels and demographic risk factors. This synthesis aims to improve the targeting of countermeasures and enhance the understanding of alcohol’s specific effects on motorcycle operation, distinct from automobile driving.

Key finding

The highest priority methodologies for future research were identified as Simulation studies, Induced Exposure studies, and Contemporary Case Control studies.

Methodology

review

Provenance

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Topics

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• induced exposure
• motorcyclist skill
• causation analyses
• incidence prevalence
• alcohol

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: crash risk outcomes
• Methodological Resource: dataset resource