Ignition Locks Effective for First-Time DUI Offenders

Devices Save Lives, Reduce Repeat Offenders

Key on table
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Laws that require first-offender drunk drivers to install ignition interlock devices on their vehicles are effective in reducing repeat DUI offenses and reducing the number of drunk driving-related fatalities.

A study of more than 19,000 first-time drunk driving offenders found that interlocks that prevent the vehicle from starting if the driver has been drinking can dramatically reduce driving while intoxicated charges.

The breath-testing devices reduced drunk driving charges by 60 percent compared to first-offenders who did not install the devices.

The study examined the records of 1,461 first time DWI offenders who had interlocks installed in their vehicles. The researchers compared them to 17,562 first offenders who did not use the devices. The two groups were matched up by age, gender, and blood alcohol concentration (BAC) at the time of arrest.

Less Likely to Repeat Offense

"We found that first-time offenders who had interlock devices were 60 percent less likely to have a repeat offense than those who did not use interlock devices," said Paul Marques, Ph.D., with the Pacific Institute for Research and Evaluation. "This study on first-time offenders reinforces prior studies on this issue that show a 65 percent reduction in drunk driving while interlocks are installed."

Marques estimated that for every dollar spent on interlocks for first offenders, the public saves $3.

First Offender: First Time Caught

Several states have laws that mandate ignition interlock devices for those convicted of first offense drunk driving. Mothers Against Drunk Driving and other advocacy groups are urging other states to pass mandatory interlocks.

"The idea that there should be any important difference between the risk posed by a first offender and a repeat offender is unsupported," Marques said in a news release. "The average first offender has driven drunk many times before he or she was arrested. The big risk difference is between non-offenders and first offenders. The risk difference between first offenders and repeat offenders is small by comparison."

Suspending Licenses Does Not Work

Research shows that merely suspending the driver's license of a convicted drunk driver does little to reduce repeat offenses. According to the Transportation Research Board of the National Research Council, an estimated 50 to 75% of offenders with suspended licenses continue to drive anyway.

On the other hand, interlock devices have been shown effective. According to a Centers for Disease Control and Prevention report, the devices are effective in reducing repeat DUI offenders by 67%, which translates into lives saved.

Opportunity to Change Behavior

"For so many years we've managed DWIs as criminals, but this is more than just a crime issue since many DWI offenders are alcohol dependent. Interlocks present an opportunity to help change behavior rather than simply punishing or incarcerating the offender," Marques says.

"It's not enough to revoke a license — 75 percent of all people with revoked licenses drive anyway — but you don't want to sentence an entire family to poverty if they're dependent on that driver getting to and from his or her job. By installing an interlock, the risk that the DWI offender poses is controlled, and interlocks become a public benefit," he said.

The most important public benefit is saved lives. According to the National Highway Traffic Safety Administration's FARS Data from 2006-2011, states that required ignition interlock devices for all convicted drunk drivers — Arizona, Louisiana, New Mexico and Oregon — saw a reduction in alcohol-related driving fatalities of 30%.


Centers for Disease Control. "Reducing Alcohol -Impaired Driving: Ignition Interlocks." Guide to Community Preventive Services 2011.

Peck, RR, et al. "Strategies for Dealing with the Persistent Drinking Driver." Transportation Research Board, Transportation Research Circular No. 437 Washington, D.C.: National Research Council, 1999.

Roth, R, et al. "Interlocks for First Offenders: Effective?" Traffic Injury Prevention 2007.

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