Modeling Trends and Projections of Riding with Alcohol-Impaired Drivers in Fatal Crashes among Young Adults: A System Dynamics Approach.

Objective: The purpose of the study was to investigate factors contributing to the decline in the number of passengers riding with alcohol-impaired drivers involved in fatal crashes since 1982, and to examine the impact of simulated interventions on this group through 2050.

Method: Historical data were obtained from the Fatality Analysis Reporting System. We applied linear regression to analyze changes in the average numbers of passengers per alcohol impaired young driver involved in fatal crashes between 1982 and 2020 by age and sex. We also extended our existing system dynamics simulation model developed to examine driving while impaired (DWI) behaviors of U.S. male and female drivers aged 15 to 24 and explored riding with an impaired driver (RWI) behaviors and corresponding interventions. We conducted sensitivity analyses to examine the likely trajectories of alcohol impaired drivers' passengers in fatal crashes across multiple scenarios through 2050.

Results: Our findings show that the decline in passengers of alcohol impaired drivers in fatal crashes primarily stems from a decrease in the number of impaired drivers, rather than a change in average number of passengers per impaired drivers. The simulation model replicated historical trends from 1982 to 2020, and the sensitivity analyses show that the policies reducing DWI trips also decrease RWI trips.

Conclusions: Wide adoption of a comprehensive strategy, combining increased enforcement, an alcohol truth campaign, the provision of alternative transportation, and the enactment of a new DWI restrictive law, could significantly reduce the number of passengers in fatal crashes involving alcohol-impaired drivers, while minimizing possible unintended consequences.