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 months1. States can levy penalties on offenders for failure to install devices2.
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 installed1, 3. When removed, however, re-arrest rates are similar to those convicted of alcohol-impaired driving who do not use interlocks1, 3, 4. Ignition interlock devices have also been shown to reduce alcohol-related crashes5, 6, 7.
Drivers with interlocks appear to have fewer alcohol-related crashes than drivers whose licenses have been suspended for an alcohol-impaired driving conviction1, 4. 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) only5, 6, 8. A Washington-based study also indicates that interlock installation requirements for first-time offenders decreases recidivism and crashes7.
Impact on Disparities
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 higher9.
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1 CG-Motor vehicle injury - The Guide to Community Preventive Services (The Community Guide). Motor vehicle injury prevention.
2 CDC-Ignition interlock - Centers for Disease Control and Prevention (CDC). Increasing alcohol ignition interlock use.
3 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.
4 IAS-Anderson 2006 - Anderson P, Baumberg B. Alcohol in Europe: A public health perspective. London, UK: Institute of Alcohol Studies (IAS); 2006.
5 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.
6 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.
7 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.
8 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.
9 MADD-Ignition interlock 2017 - Mothers Against Drunk Driving (MADD). 2017 Ignition interlock report. 2017.
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