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Last week the California Department of Motor Vehicles released study results evaluating the specific deterrent effects of California Assembly Bill 91. This law established a mandatory ignition interlock device (IID) program in four California counties: Los Angeles, Sacramento, Alameda, and Tulare.

The study looked at data from all DUI offender groups between July 1, 2010, and January 1, 2016. Per AB 91 defines the duration for IID supervision based on the number of prior DUI convictions, ranging from 5 months for the first-time DUI offense to 48 months for a fourth or any subsequent DUI violations.

According to the researchers, the study showed mixed results in terms of the impact on traffic safety:

  • “Pilot participants had lower DUI recidivism rates than other DUI offenders, but these lower rates significantly diminished over time.”
  • “Individuals obtaining an IID-restricted license had a higher increase in crashes, including fatal/injury crashes, compared to DUI offenders whose licenses remained suspended or revoked.”

This recidivism conclusion is consistent with previous studies over the last two decades that have shown recidivism rates drop during IID program supervision, but return to a rate nearly equal to DUI offenders who do not participate in an IID program. The report also notes that a 2005 California DMV study of the state’s IID program saw similar results.

IID installation rates

Interestingly, compliance with AB 91 IID installation requirements rose substantially in the pilot counties during the term of the study. Of all DUI offenders from all pilot counties combined, 42.4% installed an IID during the pilot period. In comparison, 2.1% installed IIDs during the pre-pilot period. IID installation rates in non-pilot counties peaked at 4.3% during the same period.

Based on the results of the study, officials cautioned that agencies should consider the effectiveness of IIDs as a single countermeasure. The state plans to convene a task force, including representatives from the legislature, judiciary, law enforcement, and other public agencies. The task force will develop recommendations for strengthening components of California’s comprehensive DUI countermeasure system.

There were a number of other conclusions and recommendations in the most recent report, and we will continue to cover those in future blog posts.

The full report can be found here.

What do you think of the study results?

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Kathleen Brown

Kathleen Brown

Kathleen Brown has 20+ years of experience as a public relations and marketing communications professional, including 16 years working with media, lawmakers, special interests, and government agencies on the issues of drunk driving and other alcohol-related crime. Brown first joined AMS in 2001 as an independent consultant, working with the board of directors to build private equity for final R&D and product launch of the first generation of SCRAM. She joined the staff full-time in 2004. She has worked extensively with the news media as a topic expert for industry data and research studies, community corrections, monitoring technologies, drunk driving, alcohol misuse, and the judicial system. She is currently director of Marketing & Public Relations for AMS.