UC Berkeley

Introduction

This trial assesses the effects of a community-level alcohol prevention intervention in California on alcohol-related motor vehicle crashes.

Study design

The study is a group RCT with cities as the unit of assignment to condition and as the unit of analysis.

Setting/participants

A total of 24 California cities with populations between 50,000 and 450,000 were chosen at random and roughly matched into pairs before randomly assigning 12 each to the intervention and control conditions.

Intervention

The intervention, aimed at reducing excessive drinking among adolescents and young adults, included driving under the influence sobriety checkpoints, saturation patrols, and undercover operations to reduce service of alcohol to intoxicated patrons in bars, all including high visibility so the public would be aware of them. A measure of overall intervention intensity or dosage was created.

Main outcome measures

The outcome was a monthly percentage of all motor vehicle crashes that were single vehicle nighttime crashes for drivers aged 15-30 years.

Results

Multilevel analyses were conducted to examine intervention effects on alcohol-related crashes among drivers aged 15-30 years. Crash data were obtained in 2018 with data preparation and analysis conducted in 2019. Intent-to-treat analyses indicated a 17% reduction in the percentage of alcohol-involved crashes among drivers aged 15-30 years relative to controls, which translates to about 310 fewer crashes. Dosage was found to have a statistically significant effect on crashes among this age group, although not in the expected direction.

Conclusions

Enhanced alcohol enforcement operations involving both community health and law enforcement agencies can help to reduce alcohol-impaired driving and related consequences among young people. Including measures of intervention dosage raises interesting questions about the understanding of the impact of the community intervention. Future studies should continue to further develop implementation strategies that may more effectively and efficiently reduce community alcohol-related harm.