Ignition Interlock Laws for Convicted Drunk Drivers

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ORIGIN: Cochrane Collaboration

Publication Date: 12/07/2009

Author(s): NPO Staff

The Problem:

The operation of motor vehicles while intoxicated is a major public health problem. Each year in the United States roughly 13,400 people die and an additional 255,500 are injured in motor vehicle crashes involving an alcohol-impaired driver. In 2006, these crashes accounted for almost a third of all U.S. traffic-related deaths. CDC: Impaired Driving Factsheet.

The Law:

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 blood alcohol content (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 a Cochrane Collaboration expert panel, ignition interlock programs reduce drunk-driving recidivism, but only while the devices are attached. 

Additional Information:

Mothers Against Drunk Driving (MADD) maintains an online table listing the states with ignition interlock laws.

Additional Resources: Mothers Against Drunk Driving

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