Drunk driving study: Car interlock devices reduce repeat offenses

Drunk drivers receiving their first conviction were less likely to repeat the crime if they were forced to have alcohol interlock devices on their vehicles, according to an insurance industry study.

The Insurance Institute for Highway Safety studied driver records for people with convictions related to alcohol-impaired driving in Washington. When the state expanded its interlock requirement to everyone convicted of driving under the influence eight years ago, the rate of repeat offenders fell by 12%, the study found.

Previously, Washington required the device, which a driver must blow into before starting the vehicle, for repeat offenders, drivers caught with high blood alcohol levels and those who refused an alcohol test.

“Drivers with previous impaired-driving convictions are overrepresented in alcohol-related fatal crashes, so deterring people from reoffending is a good first step to reduce the death toll,” said Anne McCartt, the institute’s senior vice president for research and the study’s main author. “As this study shows, the more offenders are covered by an interlock law, the better it works.”

The institute is supporting federal legislation that would push states to require interlocks as a result of all impaired-driving convictions, by linking receipt of federal highway funds to such action. Opponents say the device should only be used for repeat offenders and people with alcohol levels almost double the legal limit.


Washington is one of 15 states that require everyone convicted of drunk driving to install an interlock for some period of time if they want to drive, the insurance group said. Twenty-two other states require the device for repeat offenders and those with high blood alcohol levels.

California has a pilot program in four counties -- Alameda, Los Angeles, Sacramento and Tulare -- that requires first-time offenders to use the interlock device.

The institute said it believes that interlock devices present a greater obstacle to drunk driving than penalties such as a driver’s license suspension.

“It’s easier to drive illegally with a suspended license than it is to defeat an interlock,” McCartt said.


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