For over four years now in California, ignition interlock installations are required after an arrest for driving under the influence of alcohol (even  for first-time offenses) if the driver wants to avoid a temporary suspension of his or her license to drive and mandatory for almost all D.U.I. convictions. The ignition interlock law has been heralded as a “win-win.” The law allows a driver to avoid a suspension of driving privileges and makes it near impossible for that driver to drive under the influence of alcohol as long as the device is installed.

But, how effective has the mandatory ignition interlock device (IID) law been in decreasing drunk drivers and more importantly, decreasing the frequency and severity of DUI-related crashes, injuries, and fatalities?

IIDs have been ordered upon the discretion of the court for many years, and in recent years, these installations have become mandatory in many states, as in California. California actually lags in this respect; by 2013, eighteen states had already made IIDs mandatory for all drunk-driving convictions. According to the CDC, IIDs reduce repeat offense driving under the influence of alcohol by 70%….while they are installed.  Data gathered from these eighteen states suggest approximately 15% fewer drunk-driving related traffic fatalities in a study published in the American Journal of Public Health. The CDC also cites more recent studies that indicate up to 26% reduction in alcohol-related fatal crashes in states requiring an IID upon conviction of driving under the influence of alcohol.

According to the US National Highway Traffic Safety Administration, installation of IIDs had a 75% reduction in DUI arrests as compared to offenders who did not install an IID. Unfortunately, that effect disappeared when the IID was removed. A study conducted in California also found that the reduction in recidivism diminished once the IIDs were removed.

The Mineta Transportation Institute, California State University Transportation Consortium, designed an evaluation plan to evaluate whether the California IID laws can be expected to affect the frequency and severity of alcohol-related crashes. The evaluation will be conducted next year and will include a meta-analysis of research and studies since 2012, both in the US and abroad, on the impact of IID use and laws. The study will be extensive and will review data down to specific endpoints such recidivism after IID installation and DUI injuries and fatalities. The study hopes to answer whether the IID laws in effect in California can be expected to result in significant changes in the number and severity of drunk driving-related crashes and how the IID program will affect DUI recidivism.

The upshot from most of the research and studies thus far (and there are many is that IIDs are very effective in preventing drunk driving and drunk-driving related incidents as long as the IID is installed. While installation of an IID prevents a driver from firing up the engine if under the influence of alcohol and thus prevents an otherwise potential drunk-driving incident, IIDs do not appear to be a long-term solution to the problem of driving under the influence; at least at this juncture. Hopefully the Mineta Transportation Institute study will offer a definitive conclusion, which could effectively direct California public policy and law.

Orange County DUI defense attorney William Weinberg offers a complimentary consultation to review your DUI-related matter. He will review the specifics of your case and offer his opinion on your options. His goal is to achieve the best outcome possible for you. You may contact him at his Irvine office at 949-474-8008 or by emailing him at