The only ‘safe’ amount of alcohol before driving is zero, researchers prove

Posted on May 19th, 2014 by James Luckhurst

Drink driveEven “minimally impaired” drivers are more often to blame for fatal car crashes than the sober drivers they collide with, reports a study of accidents in the United States. Led by UC San Diego sociologist David Phillips and published in the British Medical Journal group’s Injury Prevention, the study examined 570,731 fatal collisions, from 1994 to 2011. The researchers used the official U.S. Fatality Analysis Reporting System (FARS) database for the study, because it is nationally comprehensive and because it reports on blood alcohol content (BAC) in increments of 0.01%. They focus particularly on drivers with BACs of 0.01 to 0.07%, and, within this group, drivers at very low BAC (0.01%).

Phillips and his co-authors found that drivers with BAC 0.01% – well below the British and US legal limit of 0.08 – are 46% more likely to be officially and solely blamed by accident investigators than are the sober drivers they collide with. The authors also found no “threshold effect” – “no sudden transition from blameless to blamed” at the legal limit for drink driving. Instead, blame increases steadily and smoothly from BAC 0.01 to 0.24%.

The researchers measured culpability for crashes by looking at more than 50 driver factors coded in the FARS database, including such “unambiguous” factors as driving through a red light or driving on the wrong side of the road. Many of the study’s analyses take advantage of what the authors call a natural experiment: two vehicle collisions between a sober and a drinking driver. “Because the two drivers collide in exactly the same circumstances and at exactly the same time,” they write, “this natural experiment automatically standardises many potentially confounding variables,” including weather and roadway conditions.

“The findings are unequivocal,” Phillips said, adding, “We find no safe combination of drinking and driving – no point at which it is harmless to consume alcohol and get behind the wheel of a car. Our data support both the National Highway Traffic Safety Administration’s campaign that ‘Buzzed driving is drunk driving’ and the recommendation made by the National Transportation Safety Board, to reduce the legal limit to BAC 0.05%. In fact, our data provide support for yet greater reductions in the legal BAC.”