Ignition interlocks help prevent drivers who were previously arrested for driving while intoxicated (DWI) from being re-arrested, according to researchers at the Centers for Disease Control and Prevention.

The researchers in CDC's Community Guide branch base that on a systematic review of 15 scientific studies on ignition interlocks. Researchers found that after these devices were installed, re-arrest rates for alcohol-impaired driving decreased by a median of 67 percent relative to drivers with suspended licenses. The review is in the March issue of the American Journal of Preventive Medicine.

Ignition interlocks are devices that can be installed in vehicles to prevent someone from operating a vehicle with a blood alcohol concentration (BAC) above a specified level. This level is usually 0.02 to 0.04 grams per deciliter (g/dL); the minimum illegal BAC level is 0.08 g/dL in every state. The devices work by sampling the driver's breath before the vehicle can be started and periodically while it is operating.

Interlocks are most often used to prevent impaired driving by people who have already been convicted of DWI. They may be mandated through the court system or offered as an alternative to a suspended driver's license. The Task Force on Community Preventive Services, an independent nonfederal body of public health experts, 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.

Impaired-driving crashes resulted in nearly 11,000 deaths in the United States in 2009—nearly one third of all traffic deaths. The annual cost of impaired driving is more than $110 billion. Preventing impaired driving and the injuries and deaths that it can cause is a priority for CDC.

"Each day, more than 30 people die because of alcohol-impaired driving. We know that interlock devices can save lives," said CDC Director Thomas R. Frieden, M.D., M.P.H. "More widespread use of ignition interlocks will reduce alcohol-related crash deaths and injuries."

As of December 2010, 13 states require interlocks for all convicted offenders, including a first conviction. More than half of all states require some offenders—such as those with multiple convictions, or an extremely high BAC at the time of arrest—to install ignition interlocks. Nonetheless, only a small proportion of DWI offenders participate in interlock programs, and according to the authors' greater use of interlocks will be needed if they are to meet their potential for reducing impaired driving. "When offenders' licenses are suspended, they aren't legally able to provide transportation for themselves and others who may rely on them to get to places like school and work," said Randy Elder, Ph.D., scientific director of systematic reviews with the Community Guide branch and lead author on the review. "Ignition interlocks allow offenders to keep operating their vehicles legally. At the same time, they effectively ensure that they do so more safely—not under the dangerous effects of alcohol." CDC recommends:

• More widespread use of interlocks.
• Ignition interlocks for everyone convicted of DWI, even for first convictions.

Full-text versions of the evidence review are available online at www.thecommunityguide.org.

CDC is also releasing "Policy Impact: Alcohol-impaired Driving," one in a series of briefs highlighting key public health issues and important science-based policy actions that can be taken to address them. Through this new publication, CDC supports state-based efforts to strengthen policies related to preventing alcohol-impaired driving. Learn more at www.cdc.gov/motorvehiclesafety/alcoholbrief.

CDC's Injury Center works to protect the safety of everyone on the road, every day. For more information about impaired driving and motor vehicle safety, please visit www.cdc.gov/motorvehiclesafety. For more information about this review, see www.thecommunityguide.org.

Background on The Community Guide

The Guide to Community Preventive Services is a resource for people who want to know what works in public health. It provides evidence-based recommendations and findings about public health interventions and policies to improve health and promote safety. The Task Force on Community Preventive Services, an independent, nonfederal body of public health and prevention experts, makes these findings and recommendations based on systematic reviews of scientific literature conducted under the auspices of the Community Guide. CDC provides ongoing scientific, administrative and technical support for the Task Force.