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Status Report, Vol. 42, No. 10 | October 13, 2007 Subscribe

Reducing BACs to the legal limit could save almost 9,000 lives a year

Police can't catch every impaired driver — or even come close. Despite their vigilance, the chance of getting arrested for driving with an illegal blood alcohol concentration (BAC) is 1 in 50 or less. This is why efforts are ongoing to go beyond traditional enforcement and succeed in deterring potential DWI offenders before they drive.

"Police enforcement always will be essential, but it's just not enough. There aren't enough officers, and we as a society may be approaching the limits of the resources that we're willing to direct to DWI," says Adrian Lund, Institute president and lead author of a new study that quantifies the death toll from crashes involving drivers impaired by alcohol. The study also discusses countermeasures that go beyond traditional methods of catching DWI offenders one by one.

Death toll from DWI

About 15,000 people died in crashes during 2005 in which one or more of the drivers had measurable BACs. But this toll isn't the same as saying that alcohol caused all 15,000 deaths. The new Institute study estimates that 13,452 crash deaths in 2005 were directly attributable to alcohol in drivers' blood. The remainder of the deaths in crashes involving alcohol would have occurred anyway, even if the drivers hadn't been drinking.

Using established methods of describing the relationship between BACs and fatal crashes, the researchers estimated the number of lives that would have been saved if all drivers' BACs were restricted to specified thresholds. Besides estimating that more than 13,000 lives would have been saved in 2005 if drivers had been restricted to no blood alcohol, the researchers estimated a saving of 8,916 lives by reducing BACs to less than 0.08 percent, the legal limit in every state, and 11,100 lives by reducing drivers' BACs to less than 0.05 percent.

About 1,200 crash deaths in 2005 involved drivers who had both measurable BACs and DWI convictions on their records during the preceding 3 years. If these drivers' BACs had been zero, about 1,100 lives would have been saved.

"Not every drinking driver gets into a crash, and all crashes wouldn't be eliminated if every driver were alcohol free," Lund points out. "Still the findings indicate the vast potential to save lives by reducing drivers' BACs."

All drivers
Lives that would be saved by reducing their BACs to

...less than 0.08% 8,916
...less than 0.05% 11,100
...zero BAC 13,452

Note: zero BAC defined as less than 0.02%

Drivers with 1+ prior
Lives that would be saved by reducing their BACs to

...less than 0.08% 777
...less than 0.05% 944
...zero BAC 1,104

Jump-start is needed

Progress was made during the 1980s and early 1990s to reduce crashes involving alcohol impairment. In particular, policies to suspend offenders' licenses on the spot, without a court conviction, began reducing crashes in the mid-1980s (see "MADD campaign will use new study," April 16, 1988).

A 2007 study by researchers at the University of Florida indicates that this policy has reduced deaths in crashes involving drivers with illegal BACs ("Effects of drivers' license suspension policies on alcohol-related crash involvement: long-term follow-up in forty-six states" by A.C. Wagenaar et al. is published in Alcoholism: Clinical and Experimental Research 31:8:399-406).

Results of other policies have been modest, and worldwide progress against alcohol-impaired driving has stalled (see Status Report special issue: alcohol-impaired driving, April 2, 2005). One reason is that countermeasures known to be effective aren't being widely applied. For example, research shows that sobriety checkpoints reduce fatal crashes involving drivers with high BACs. But for a variety of reasons checkpoints aren't widely conducted (see "Sobriety checkpoints work, but they aren't used often," June 30, 2001).

Another example is alcohol interlocks, devices that prevent drivers with proscribed BACs from starting their vehicles. Institute research indicates the effectiveness of this approach (see "Ignition interlocks reduce rearrest rates of alcohol offenders," Jan. 15, 2000), and about 100,000 interlocks are in use in North America. The downside is that available interlock devices are intrusive, so their use mostly has been limited to repeat offenders who represent only a fraction of all impaired drivers.

Goal is to deter, not just apprehend

Interlocks would be "the ultimate deterrent if they could be applied to every driver," Lund says. "Then we wouldn't have to try to convince impaired drivers not to take to the road. We could use technology to prevent them from doing so, and we could save as many as 9,000 or so lives each year."

A symposium was convened in 2006 to consider advanced interlock technologies. Since then a Blue Ribbon Panel for the Development of Advanced In-Vehicle Alcohol Detection Technologies has been organized to develop interlocks that will be suitable for all drivers, not just those already convicted of DWI. Challenges for the panel include addressing not only the devices' accuracy but also how quickly and unobtrusively they measure BACs (see Status Report special issue: alcohol-impaired driving, April 2, 2005). It will be important not to inconvenience the vast majority of drivers who haven't consumed any alcohol.

"This is the way to go. It's better to prevent people from breaking the law, and perhaps killing or injuring someone, than to arrest offenders after the fact. Punishing the few impaired drivers that our limited police resources can catch won't bring back the lives taken by the drivers who went undetected," Lund concludes.

Other researchers weigh in on contribution of alcohol to crashes

A study from the Pacific Institute for Research and Evaluation estimates that 15 to 26 percent of crashes between 4 pm and 2 am could be prevented if nobody drove with a BAC any higher than 0.04 percent. Like the Institute study, this one separates alcohol's contribution to crashes from the other factors that might be contributing to the crashes involving alcohol and points to improvements that could be achieved by reducing or eliminating alcohol from drivers' blood. The report, "Improved methods for estimating relative crash risk in a case-control study of blood alcohol levels," by R.C. Peck et al. was presented at a meeting of the International Council on Alcohol, Drugs, and Traffic Safety, held in Seattle in August.

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