Relative Risk of Fatal Crash Involvement by Bac, Age, and Gender

Objective: To reexamine and refine estimates for alcohol-related relative risk of driver involvement in fatal crashes by age and sex as a function of B AC using recent data. Methods: Logistic regression was used to estimate age/sex specific relative risk of fatal crash involvement as a function of the BAC of fatally injured and surviving drivers by combining crash data from the Fatality Analysis Reporting System with exposure data from the 1996 National Roadside Survey of Drivers. Results: In general, the relative risk of involvement in a fatal passenger vehicle crash increased steadily with increasing driver BAC in every age/sex group among both fatally injured and surviving drivers. A 0.02 percentage point BAC increase among 16-20 year old male drivers was estimated to more than double the relative risk of fatal single vehicle crash injury. At the mid-point of the 0.08%-0.10% BAC range, the relative risk of a fatal single-vehicle crash injury varied between 11.4 (drivers 35 and older) and 51.9 (male drivers, 16-20). With only very few exceptions, older drivers had lower risk of being fatally injured in a single vehicle crash than younger drivers, and females than males in the same age range. When comparable, results largely confirmed existing prior estimates. Conclusions: This is the first study that systematically estimated relative risk for drinking drivers with BACs between 0.08% and 0.10% (these relative risk estimates apply to BAC range mid-points at 0.09%). The results clearly show that drivers at non-zero BACs somewhat below 0.10% pose highly elevated risk both to themselves and to other road users. Section Page 1 Introduction and Background 1 2 Methods 2 3 Results 5 4 Discussion 9 5 References 18 List of Appendices A Weight adjustments to the exposure data A B Driver selection from FARS B C Logistic regression models C D Fay's method for generating replicate weights D E Estimating design-based variances in the presence of multiply imputed BACs E F Alternative models logistic regression models for involvement/exposure ratios F iii Table of Contents (continued) List of Figures Relative fatality risk for drinking drivers by age and sex in single vehicle crashes 8 Relative risk for the involvement of drinking drivers by age and sex in all passenger vehicle crashes 8 Baseline risk at BAC=0 relative to male 21-34 group 11 List of Tables Table Page 1.1 Exposure survey sample size (N) and weighted percent distribution (%) by sex, age, and …