Laws requiring all impaired-driving offenders to install alcohol interlocks reduce the number of impaired drivers in fatal crashes by 16 percent, a new IIHS study shows. If all states without such laws adopted them, more than 500 additional lives could be saved each year.
A separate study shows that those laws could be made even more effective. In a detailed examination of Washington’s interlock policies, Institute researchers found that, as the state’s interlock laws were strengthened, interlock installations went up and recidivism declined. At the same time, more DUI charges were reduced to lesser offenses that don’t require interlocks. That suggests states could increase the impact of their interlock laws by closing such loopholes.
The two studies are the latest to support the expansion of alcohol interlocks — in-vehicle breath-testing units that require a blood alcohol concentration (BAC) below a certain level, typically somewhere between 0.02 and 0.04 percent, before the vehicle can be started.
More than a quarter of U.S. crash deaths occur in crashes in which at least one driver has a BAC of 0.08 percent or higher. The prevalence of impaired driving in fatal crashes has changed little in the past two decades, and interlock laws are one of the few recent policy innovations that have made a difference.
Forty-five states require interlocks for at least certain impaired-driving offenders. Twenty-eight states, the District of Columbia and four California counties have some type of interlock requirement that applies to first-time offenders.
Even when they are mandated for first offenders, interlocks come into play only after a DUI arrest, so their direct purpose is to reduce recidivism. Like other types of sanctions, however, they may act as a deterrent for those who haven’t yet committed a first offense if they are well-publicized.
…For the analysis, the authors grouped together two types of all-offender interlock laws: those that require all offenders, including first-time offenders, to install interlocks in order to have their license reinstated and those that only require it to drive during a post-conviction suspension. The analysis controlled for factors besides interlocks that could affect crashes.
Laws that required interlocks for repeat offenders only cut the number of drivers with BACs of 0.08 percent by 3 percent compared with no interlock law, and that effect wasn’t statistically significant, the study showed. Laws that required them for both repeat offenders and offenders with high BACs provided an 8 percent benefit.
Read the entire story at the IIHS website at: http://www.iihs.org/iihs/sr/statusreport/article/53/2/1