ANN ARBOR—While Michigan’s newest drunk-driving laws have helped reduce alcohol-related traffic deaths by as much as 25 percent since 1992, the measures have had little impact on repeat offenders, says a University of Michigan researcher.

In his study of 56 drunk drivers convicted in 1992 and 1993, David Eby, an assistant research scientist at the U-M Transportation Research Institute, found that nearly half had at least one other drinking and driving conviction in the previous 10 years and 15 percent had at least two prior alcohol convictions during that time.

“The study revealed a high drunk-driving recidivism rate among offenders, which suggests that the current drunk- and impaired-driving laws in Michigan are not having a strong, specific deterrent effect on individuals with a history of drinking and driving,” Eby says.

About 55 percent of the drunk drivers in the study’s sample had at least one previous crash (although not necessarily alcohol-related), 43 percent were classified as ‘unacceptable’ or ‘problem drivers’ (according to Eby’s Index of Past Driving Competence), and 30 percent were driving with a restricted, suspended, revoked or expired license.

“These data indicate that those who are driving drunk also tend to violate other driving laws and be involved in traffic crashes,” Eby says. “Further, it appears that a large percentage of these people do not change their poor driving behaviors in response to license sanctioning.”

Because 30 percent to 70 percent of perpetrators may still choose to drive—albeit illegally—after losing their licenses, Eby believes that also impounding or immobilizing their vehicles during the sanction period would be more effective than simply suspending or revoking their licenses.

In addition to the need for tougher licensing sanctions, Eby found that most courts usually follow at least the minimum sentencing guidelines for convicted drunk drivers. However, more than a third receive a lesser conviction than warranted based upon their driving record— thanks to plea bargaining.

The study also shows that about 88 percent of convicted drunk drivers become inebriated in public (in restaurants, bars or their vehicles) prior to their arrest, underscoring the need for stronger enforcement of “alcohol-server” laws, which make it illegal to serve alcohol to already-drunk patrons.

As expected, Eby found that most (93 percent) arrests take place between 6 p.m. and 6 a.m. on weekends, indicating that alcohol-specific enforcement programs, such as sobriety checkpoints, operating at peak times have high potential for success.

Eby says that a weaving vehicle observed by police is the most common event that initially draws attention to drunk drivers, although many alerting incidents are not based upon police activity.

“In over a third of the drunk-driving arrests in the sample, the drunk driver was first identified because of a crash or because a citizen contacted law enforcement,” Eby says. “This result clearly reflects the important role citizens have in combatting drunk driving.”

Finally, Eby recommends that the minimum blood-alcohol level for drunk driving be lowered from 0.10 percent to 0.08 percent, and that state driver-licensing agencies examine more closely a driver’s history before issuing a new license.