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Effects of Washington state's alcohol ignition interlock laws on DUI recidivism: an update

McCartt, Anne T.; Leaf, William A.; Farmer, Charles M.
Insurance Institute for Highway Safety
March 2018

Objective: To examine the effects of changes to Washington state's alcohol ignition interlock laws: moving issuance of interlock orders from the courts to the driver licensing department (July 2003); extending the interlock order requirement to all persons convicted of DUI (June 2004); allowing an interlock in lieu of an administrative driver's license suspension (January 2009); and requiring proof of interlock installation to reinstate the driver's license (January 2011).
Method: Trends in conviction types, interlock installation rates, and 2-year cumulative recidivism rates were examined for first-time and repeat convictions stemming from DUI arrests during 1999-2012. ARIMA models examined the association between law changes and interlock installation rates, law changes and 2-year recidivism rates, and interlock installation rates and 2-year recidivism rates.
Results: During the study period, there was a large increase in the proportion of first-time DUI arrests reduced to alcohol-related negligent/reckless driving, offenses not requiring interlock orders. The rate of interlock installations increased substantially and the rate of recidivism declined substantially among both first and repeat offenders. Based on the ARIMA models for first offenders, the 2004 and 2009 law changes were associated with increased interlock installation rates and lower recidivism rates. The 2011 law change was associated with a nearly significant decline in the interlock installation rate (P = 0.0869) and a marginally significant reduction in recidivism (P = 0.0527). For first offenders arrested during the last quarter of 2012, the model estimates a 26 percent reduction in the recidivism rate (from an expected 7.7 percent without the law changes to 5.6 percent). A 1 percentage point increase in the interlock installation rate was associated with a 0.06 percentage point decline in the recidivism rate among first offenders. If the association carried forward and if the installation rate had been 100 percent rather than 38 percent in the last quarter of 2012, the 2-year recidivism rate would have been reduced from 5.6 to 2 percent. Among repeat offenders, the 2003 and 2009 law changes were associated with increased interlock installation rates, and the 2009 law change was associated with a nearly significant decline in recidivism (P = 0.0704).
Conclusions: In Washington, rates of interlock installations increased as interlock laws were strengthened, and the increase was associated with reductions in recidivism among first DUI offenders. Washington's experience suggests that states can reduce DUI recidivism by requiring interlock orders for all offenders, allowing offenders to install interlocks in lieu of an administrative driver's license suspension, and closing statutory loopholes that allow plea reductions to convictions without interlock orders.