The Impact of Ignition Interlock Laws on DUI Arrests

We study the impact of Ignition Interlock Laws (IILs), an increasingly popular public policy aimed at reducing drunk driving, on driving under the influence (DUI) arrests. While past studies have found that IILs reduce alcohol-impaired motor vehicle fatalities and short-term recidivism rates, little evidence exists on how IILs impact DUI arrests as a more direct indicator of DUI prevalence. Using state-level monthly panel data from the Uniform Crime Reporting Program, we find that DUI arrests decrease in response to IIL adoption, though more substantively and significantly when all DUI offenders are required to use them for a period after their conviction. The results suggest deterrence may be at least partially responsible for this effect, contrary to what a previous analysis of motor vehicle fatalities concluded. Our results add to the understanding of how IILs work, as policy makers continue to address the over 100 million episodes of driving while potentially under the influence of alcohol that are reported annually.