Publication Date: 
Wednesday, July 31, 2019

The Problem: In 2016, roughly 10,500 people died in motor vehicle crashes involving an alcohol-impaired driver, accounting for nearly one-third of all traffic related deaths. CDC: Impaired Driving Factsheet. Approximately 6,500 (62%) of these individuals had a blood alcohol content (BAC) level of 0.08 g/dL or greater. The remaining fatalities consisted of passengers (29%) and non-passengers (9%). NHTSA: Alcohol-Impaired Driving

The Law: All 50 states, the District of Columbia, and Puerto Rico have legal thresholds that set a BAC of 0.08 g/dL or greater as illegal alcohol-impaired driving. In an effort to reduce drunk-driving recidivism, municipalities and states have experimented with ignition interlock programs. Ignition interlock devices disable a car’s ignition until the driver provides a breath sample that confirms that the driver’s (BAC) is under the requisite limit. Participation in ignition interlock programs is sometimes required as a condition of sentences for violating drunk- driving laws. Initially, participation in the US was generally on a voluntary basis (e.g., violators could participate to regain their driving privileges earlier than otherwise provided) or was left to the court’s discretion and implemented only for repeat offenders. For examples of ignition interlock laws, see 75 Pa.C.S. §§ 88.1-88.8 (Pennsylvania), 90 MGL 24(c)(2) (Massachusetts), and A.R.S. §28-1381(I)(6) (Arizona).

The Evidence: In a systematic review, Willis et al. reviewed 14 studies in the U.S. and Canada evaluating the effects of ignition interlock programs on drunk-driving recidivism. Willis et al. Alcohol ignition interlock programmes for reducing drink driving recidivism. Cochrane Database of Systematic Reviews. 2004; Issue 3. The underlying studies measured three types of outcomes: (1) recidivism rates while the driver participated in the ignition interlock program, (2) recidivism rates after the ignition interlock device was removed from the vehicle, and (3) recidivism rates during the entire study period. The reviewers found that interlock program participants were less likely to repeat offend than the control group. The impact was even more pronounced for repeat offenders. However, in each instance, recidivism returned to pre-intervention rates after the devices were removed. Though effective as a short-term intervention, continued research on the effects of ignition interlock programs on drunk-driving recidivism over longer time periods is needed.

The Bottom Line: In the judgment of the authors, ignition interlock programs may be beneficial, but require additional research for confirmation.

Additional Resources: Mothers Against Drunk Driving

 Impact: Uncertain