Sobriety Checkpoints and Alcohol-Involved Motor Vehicle Crashes at Different Temporal Scales

Abstract

Roadside sobriety checkpoints are an intervention in which law enforcement officers stop passing vehicles to check whether drivers are impaired. There is clear evidence that a program of roadside sobriety checkpoints is an effective approach to reducing alcohol-involved motor vehicle crashes, likely because of general deterrent effects across the entire population of drivers. The aim of this study is to assess the duration of time over which individual roadside sobriety checkpoints are associated with alcohol-involved motor vehicle crashes, within the context of a broader checkpoint program. In August 2018, the authors accessed incident-level data for alcohol-involved motor vehicle crashes and roadside sobriety checkpoints for the City of Los Angeles, California, 2013-2017. Counts of crashes and checkpoints were computed within three different temporal units: days (n=1,826), weeks (n=260), and months (n=60). The number of checkpoints were then calculated at different lagged periods (up to 7 days, up to 4 weeks, and up to 3 months). Autoregressive integrated moving average analyses related counts of checkpoints over these lagged periods to subsequent crashes. Fewer alcohol-involved motor vehicle crashes occurred when there were more roadside sobriety checkpoints over the previous 4 days, 5 days, 6 days, 7 days, and 1 week. Individual roadside sobriety checkpoints affected alcohol-involved motor vehicle crashes in Los Angeles, California for approximately 1 week. The temporal configuration of individual checkpoints is an important consideration when designing an overall roadside sobriety checkpoint program.