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Reducing Alcohol-Impaired Driving: Ignition Interlocks

Ignition interlocks are devices that can be installed in motor vehicles to prevent operation of the vehicle by a driver who has a blood alcohol concentration (BAC) above a specified level (usually 0.02% – 0.04%). Interlocks are most often installed in vehicles of people who have been convicted of alcohol-impaired driving to give them an opportunity to drive legally.

Summary of Task Force Recommendations & Findings

The Community Preventive Services Task Force recommends the use of ignition interlocks for people convicted of alcohol-impaired driving on the basis of strong evidence of their effectiveness in reducing re-arrest rates while the interlocks are installed. Public health benefits of the intervention are currently limited by the small proportion of offenders who install interlocks in their vehicles. More widespread and sustained use of interlocks among this population could have a substantial impact on alcohol-related crashes.

About the Interventions

The court system may mandate installation of ignition interlocks or state licensing agencies may offer them as an alternative to a suspended driver’s license for persons convicted of alcohol-impaired driving. The amount of time they are installed typically matches the period for which the license would otherwise be suspended. This most often ranges from 6 to 24 months. Typically, only a small percentage of eligible people participate in ignition interlock programs because many offenders prefer license suspension. Rates of usage, however, vary substantially based on how programs are administered.

Results from the Systematic Reviews

The Task Force recommendation was based on results from two systematic reviews that considered a total of 15 studies.

  • While interlocks were installed, re-arrest rates decreased by a median of 67% relative to comparison groups (13 studies). This estimate is based on all of the available studies that reported separate results for re-arrests during the interlock installation period.
  • When interlocks were removed, re-arrest rates reverted to rates similar to those of persons convicted of alcohol-impaired driving who had not used interlocks (11 studies).
  • Drivers with interlocks installed had fewer alcohol-related crashes than those who had licenses suspended for an alcohol-impaired driving conviction (1 study).
  • Overall crash rates for drivers with interlocks were similar to those for the general driving population. Drivers with ignition interlocks, however, had a substantially greater number of crashes overall than did drivers with suspended licenses. This is likely because those with ignition interlocks drove more than those with suspended licenses (2 studies).

The first review, conducted by the Cochrane Collaboration (Willis, Lybrand and Bellamy, 2004)*, identified 11 studies evaluating the effect of interlock installation on re-arrest rates for alcohol-impaired driving. The evidence from this review was supplemented by a follow-up review that covered a period through December 2007. This follow-up review included four additional studies and also evaluated evidence from the Cochrane Collaboration review to examine the effects of interlocks on crash outcomes.

Scientists from Centers for Disease Control and Prevention’s (CDC) Division of Unintentional Injury Prevention led this follow-up review. They received input from a team of specialists in systematic review methods and experts in research, practice and policy related to reducing alcohol-impaired driving.

* Willis C, Lybrand S, Bellamy N. Alcohol ignition interlock programmes for reducing drink driving recidivism. The Cochrane Database of Systematic Reviews 2004, Issue 3.

Supporting Materials

Publications

Elder RW, Voas R, Beirness D, Shults RA, Sleet DA, Nichols JL, Compton R, Task Force on Community Preventive Services. Effectiveness of ignition interlocks for preventing alcohol-impaired driving and alcohol-related crashes: a Community Guide systematic review. Adobe PDF File [PDF - 584KB] Am J Prev Med 2011;40(3):362–76.

Task Force on Community Preventive Services. Recommendations on the effectiveness of ignition interlocks for preventing alcohol-impaired driving and alcohol-related crashes. Adobe PDF File [PDF - 74KB] Am J Prev Med 2011;40(3):377.

Magnusson P, Jakobsson L, Hultman S. Alcohol interlock systems in Sweden: 10 years of systematic work. Adobe PDF File [PDF - 86KB] Am J Prev Med 2011;40(3):378–9.

More Community Guide publications about the Prevention of Motor Vehicle-Related Injuries

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Disclaimer

The findings and conclusions on this page are those of the Community Preventive Services Task Force and do not necessarily represent those of CDC.

Sample Citation

The content of publications of the Guide to Community Preventive Services is in the public domain. Citation as to source, however, is appreciated. Sample citation: Guide to Community Preventive Services. Reducing alcohol-impaired driving: ignition interlocks. www.thecommunityguide.org/mvoi/AID/ignitioninterlocks.html. Last updated: MM/DD/YYYY.

Review completed: April 2006