Studies Tout Safety Benefits of Expanded Ignition Interlock

The National Center for State Courts recently published an Ignition Interlock Report reviewing the latest research on ignition interlock programs. Two of the studies cited reported efficacy rates striking enough to attract the attention of any policy wonk interested in highway safety.

Requiring ignition interlock for all DWI convictions saves lives. Researchers at the University of Pennsylvania published in 2016 the results of a study comparing alcohol-involved crash deaths in states that required ignition interlock for every driver convicted of impaired driving and states that did not. Kaufan, Elinore J. & Wiebe, Douglas J., Impact of State Ignition Interlock Laws on Alcohol-Involves Crash Deaths in the United States, 106 AM. J. PUB. Health, No. 5, 865-71 (2016).

In North Carolina, only a subset of drivers convicted of impaired driving are required to have ignition interlock as a condition of having their licenses restored. Ignition interlock is required if the person had an alcohol concentration of 0.15 or more, a previous conviction for impaired driving within seven years of the offense leading to the license revocation, or was sentenced at aggravated level one. G.S. 20-17.8(a). A judge who issues a limited driving privilege to a person convicted of impaired driving with an alcohol concentration of 0.15 or more must require ignition interlock as a condition of the privilege. G.S. 20-179.3(g5). A judge awarding a limited driving privilege following any other DWI conviction may require ignition interlock in his or her discretion. G.S. 20-179.3(g3).

The authors of the aforementioned study found that requiring ignition interlock following every impaired driving conviction was associated with 15 percent fewer alcohol-involved crash deaths than occurred in states like North Carolina with less-stringent requirements. The reduction of 0.8 deaths for every 100,000 people each year was comparable, researchers noted, to airbags and raising the minimum legal drinking age, which saved 0.9 and 0.2 lives per 100,000 population, respectively. The study concluded that “[a]lthough a comprehensive solution to the problem of alcohol-impaired driving would likely require both changing the alcohol culture in the United States to reduce binge drinking and increasing access to alternative transportation, interlock devices remain a promising approach to reducing drunk driving at the individual level.” Id. at 870.

Installing ignition interlock in all new vehicles would save even more lives. A study by University of Michigan researchers published in 2015 estimated the fatalities and injuries that would be prevented if ignition interlocks were installed in all new vehicles. Carter, P.M. et al., Modeling the Injury Prevention Impact of Mandatory Alcohol Ignition Interlock Installation in All New US Vehicles, 105 AM. J. PUB. Health, No. 5, 1028-35 (2015). Researchers concluded that installing interlocks in all new vehicles would prevent, over a 15-year implementation period, 83 percent of alcohol-related crash fatalities and 84 to 88 percent of nonfatal injuries associated with drinking drivers. The injury prevention benefit was greatest for younger drivers between the ages of 20 and 29 who comprise the group most at-risk for alcohol-related crash injuries. The study also found that after three years of mandatory ignition interlock installation in all new vehicles, the financial benefit realized by preventing injury-related costs outweighed the costs of the devices.

The study’s authors noted that current ignition interlock devices lack the technological sophistication required for installation as standard equipment in new vehicles, citing their slow reading times, need for frequent calibration and mouthpiece requirements. Researchers pointed out that newer technology was under development as part of the Driver Alcohol Detection System for Safety (DADSS) program, a collaborative research partnership between motor vehicle manufacturers and the National Highway Traffic Safety Administration (NHTSA) to identify in-vehicle approaches to prevent alcohol-impaired driving.

What is the status of that new technology? Researchers published a status update on DADSS in 2017. Prototype sensors have been developed and installed in a research vehicle for testing. One sensor is designed to remotely measure alcohol concentration in a driver’s breath from the ambient air in the vehicle cabin. The other is designed to measure alcohol in the driver’s finger tissue when it is placed on a sensor. The 2017 report describes the technological and manufacturing challenges that must be surmounted before breath-based or touch-based sensors are commercially feasible, making clear that while much progress has been made, much is left to be done.

Other policy suggestions.The University of Pennsylvania researchers who authored the first study described in this post suggested an additional approach to increase ignition interlock use: incorporating ignition interlocks for young drivers as part of a graduated licensing program. Kaufman & Wiebe at 870. Another study cited in the Ignition Interlock Report also referenced a possible connection between ignition interlocks and graduated license requirements. See Kelley-Baker, T. et al., The Feasibility of Voluntary Ignition Interlocks as a Prevention Strategy for Young Drivers, Report No. DOT HS 812 425 (National Highway Traffic Safety Administration, Washington, D.C.) (June 2017). After noting the difficulty in recruiting parents to voluntarily place ignition interlock devices on vehicles driven by their children, the authors of this latter study commented that “State legislation could play a role in incentivizing young driver ignition interlocks by providing additional driving privileges based on the installation of devices.” Id. at 58. The researchers reported a consistent theme that arose in their discussions with various interest groups about voluntary ignition interlocks for young driver: Attitudes would have to shift from viewing ignition interlock as punishment to viewing them as safety devices.

4 thoughts on “Studies Tout Safety Benefits of Expanded Ignition Interlock”

  1. What a silly study. Want to stop all DUIs? Confiscate all vehicles. Of course we can reduce rates by effectively preventing the behavior. At the heart of the matter is the fundamental liberty interest in traveling unimpeded vs the state’s interest in public welfare.

    I fail to see how this study does anything other than proving an obvious point.

    Though I have no doubts that this article will eventually end up in the legislative record the next time the Politicians want to be seen as “tough on crime.”

  2. Idaho just required interlock devices following all convictions and I believe admin suspensions. WSU has been researching marijuana breathalyzers (which could be integrated into interlocks too), but halted research when the Trump admin withdrew the Cole Memo. Irony right? Research into marijuana enforcement tools halts by a perceived crackdown on marijuana research.

  3. NC DMV’s analysis of traffic fatalities in 2015 found that over 80% of NC’s fatal crashes were caused by sober drivers, not impaired drivers. (Only 19.7 % of fatal crashes involved drivers with .08 or higher BAC). There are far too many bad drivers out there. We should focus on encouraging better, safer drivers instead of acting as if drunk driving is the primary culprit of traffic deaths. We could have graduated licenses based on performance on stringent driving skill and knowledge tests. We could require lower insurance payments for people who have passed the proficiency tests for the upper-level licenses.

    We also could punish drivers who actually cause crashes more harshly than drivers who do not cause crashes but only increase the chance of causing a crash by drinking and driving. Currently we punish drivers more for increasing the chance of doing harm by driving while impaired than we punish drivers who actually do the harm by causing a crash.

  4. I understand the statistics a little different. It would be interesting to know the part, if any, that II providers played in these “studies”. Opiate impairment is on the rise and the II would do nothing to detect this impairment. Imposing a condition on innocent citizens as a condition of purchasing a vehicle is unreasonable. Experience practitioners know well the frequency with which these devices report alcohol when there is no such alcohol…only a honey bun or air freshener.


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