Ignition interlock devices

Ignition interlocks are devices that can be installed in vehicles to prevent operation by a driver who has a blood alcohol concentration (BAC) above a specified level. Interlocks are most often installed in vehicles of people who have been convicted of alcohol-impaired driving. Interlocks can be mandated by courts or offered by state licensing agencies as an alternative to a suspended driver’s license, often as a provision of a restricted license. Requirements for use of interlock devices varies by state based on BAC level, number of offenses, and other conditions. Interlocks are generally installed for the length of time a license would be suspended, usually 6 to 24 months (CG-Motor vehicle injury). States can levy penalties on offenders for failure to install devices (CDC-Ignition interlock).

Expected Beneficial Outcomes (Rated)

  • Reduced impaired driving

  • Reduced alcohol-related crashes

Evidence of Effectiveness

There is strong evidence that installing ignition interlock devices for people convicted of alcohol-impaired driving reduces re-arrest rates while interlocks are installed (CG-Motor vehicle injury, ). When removed, however, re-arrest rates are similar to those convicted of alcohol-impaired driving who do not use interlocks (CG-Motor vehicle injury, , IAS-Anderson 2006). Ignition interlock devices have also been shown to reduce alcohol-related crashes (, Ullman 2016, ).

Drivers with interlocks appear to have fewer alcohol-related crashes than drivers whose licenses have been suspended for an alcohol-impaired driving conviction (CG-Motor vehicle injury, IAS-Anderson 2006). States with laws that require interlock use for all drunk driving offenders, including first-time offenders, have greater reductions in crash rates and crash-related deaths than states with laws that require interlock use for high-risk offenders (e.g., repeat offenders) only (, , Ullman 2016). A Washington-based study also indicates that interlock installation requirements for first-time offenders decreases recidivism and crashes ().

Impact on Disparities

No impact on disparities likely

Implementation Examples

As of 2017, every state has an ignition interlock law, although specifics vary. Twenty-nine states and Washington DC have mandatory ignition interlock provisions for all convicted drunk driving offenders. Florida, Hawaii, New Jersey, North Carolina, Wisconsin, and Wyoming require ignition interlocks for first-time convicted offenders with a certain BAC level or higher (MADD-Ignition interlock 2017).

Implementation Resources

NCSL-Ignition interlock - National Conference of State Legislatures (NCSL). State ignition interlock laws.

CDC-Ignition interlock - Centers for Disease Control and Prevention (CDC). Increasing alcohol ignition interlock use.

Citations - Evidence

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CG-Motor vehicle injury - The Guide to Community Preventive Services (The Community Guide). Motor vehicle injury prevention.

IAS-Anderson 2006 - Anderson P, Baumberg B. Alcohol in Europe: A public health perspective. London, UK: Institute of Alcohol Studies (IAS); 2006.

Miller 2015c* - Miller PG, Curtis A, Sønderlund A, Day A, Droste N. Effectiveness of interventions for convicted DUI offenders in reducing recidivism: A systematic review of the peer-reviewed scientific literature. The American Journal of Drug and Alcohol Abuse. 2015;41(1):16-29.

McGinty 2017* - McGinty EE, Tung G, Shulman-Laniel J, et al. Ignition interlock laws: Effects on fatal motor vehicle crashes, 1982-2013. American Journal of Preventive Medicine. 2017;52(4):417-423.

Kaufman 2016* - Kaufman EJ, Wiebe DJ. Impact of state ignition interlock laws on alcohol-involved crash deaths in the United States. American Journal of Public Health. 2016;106(5):865-871.

Ullman 2016 - Ullman DF. Locked and not loaded: First time offenders and state ignition interlock programs. International Review of Law and Economics. 2016;45:1-13.

McCartt 2013* - McCartt AT, Leaf WA, Farmer CM, Eichelberger AH. Washington State’s alcohol ignition interlock law: Effects on recidivism among first-time DUI offenders. Traffic Injury Prevention. 2013;14(3):215-229.

Citations - Implementation Examples

* Journal subscription may be required for access.

MADD-Ignition interlock 2017 - Mothers Against Drunk Driving (MADD). Ignition interlocks: Every state, for every convicted drunk driver. 2017.

Date Last Updated

Jul 26, 2017