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, Miller 2015c*). When removed, however, re-arrest rates are similar to those convicted of alcohol-impaired driving who do not use interlocks (CG-Motor vehicle injury, Miller 2015c*, IAS-Anderson 2006). Ignition interlock devices have also been shown to reduce alcohol-related crashes (McGinty 2017*, Ullman 2016, McCartt 2013*).
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 (McGinty 2017*, Kaufman 2016*, Ullman 2016). A Washington-based study also indicates that interlock installation requirements for first-time offenders decreases recidivism and crashes (McCartt 2013*).
Impact on Disparities
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
CDC-Ignition interlock - Centers for Disease Control and Prevention (CDC). Increasing alcohol ignition interlock use.
NCSL-Ignition interlock - National Conference of State Legislatures (NCSL). State ignition interlock laws.
Citations - Evidence
* Journal subscription may be required for access.
CG-Motor vehicle injury - The Guide to Community Preventive Services (The Community Guide). Motor vehicle injury prevention.
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.
IAS-Anderson 2006 - Anderson P, Baumberg B. Alcohol in Europe: A public health perspective. London, UK: Institute of Alcohol Studies (IAS); 2006.
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.
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.
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.
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.
Related What Works for Health Strategies
To see citations and implementation resources for this strategy, visit:
countyhealthrankings.org/take-action-to-improve-health/what-works-for-health/strategies/ignition-interlock-devices
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countyhealthrankings.org/whatworks