Ignition Locks Prevent Repeat DWI Offenses

FRIDAY Feb. 15, 2008 -- Breath-testing devices that prevent a vehicle from starting if the driver's blood alcohol level exceeds a preset limit can dramatically reduce more DWI offenses among first-time offenders, a new study shows.

First offenders with "interlock" devices installed on their cars were 60 percent less likely to have a repeat offense than those who did not use the devices, according to findings published in the current issue of Traffic Injury Prevention.

"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," Paul Marques, of the Pacific Institute for Research and Evaluation, said in a prepared statement.

The findings may help resolve questions about whether interlocks work as well with first-time offenders as with repeat offenders. Two earlier studies had questioned their effect, but the researchers noted that in those studies, only a small proportion of those required to install the interlocks actually did.

In the new study, researchers examined the records of 1,461 first-time DWI offenders in New Mexico who had interlocks installed in their vehicles and compared them with 17,562 first-time offenders in the state who didn't use the devices. The two groups were matched by age, gender and blood alcohol concentration at the time of arrest.

"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," Marques said.

This research -- funded in part by the Substance Abuse Policy Research Program of the Robert Wood Johnson Foundation, a philanthropic organization that focuses on health and health-care issues -- also cited possible economic benefits to vehicle interlocks.

One device cost the offender $2.25 per day, leading the authors to estimate that for every dollar spent on interlocks for first offenders, the public saves $3 in damage and destruction caused by DWI crashes.

"Interlocks present an opportunity to help change behavior rather than simply punishing or incarcerating the offender," Marques said. "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."

Only about 10 percent of arrested DWIs nationally are ordered a period of interlock-controlled driving, Marques said. Four states mandate interlocks for first DWI offenses: New Mexico, Louisiana, Arizona and Illinois (effective in 2009).

More information

The National Institute on Alcohol Abuse and Alcoholism offers has more about preventing alcohol abuse.

Posted: February 2008


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