Many Americans can recite, even when drunk, the blood alcohol content (BAC) limit for driving is 0.08, the point at which a driver is too impaired to safely handle a vehicle. It may be time to question that assumption. A new study, published in the journal Injury Prevention, found that drivers with a BAC level as low as 0.01 are 46 percent more likely to be officially blamed for causing a crash as compared with the sober driver involved in the accident. “There appears to be no safe combination of drinking and driving — even minimally ‘buzzed’ drivers pose increased risk to themselves and to others,” the authors wrote. “Lowering the legal BAC limit is likely to reduce injuries and save lives.”

Legal Limits

Worldwide, substantial disagreement exists as to where exactly a line need be drawn between drinking and driving. In Sweden, a 0.02 BAC is considered the level that spells danger when operating a vehicle, in Japan the limit is set at 0.03, while in South Korea, Taiwan, Germany, and most countries in Europe, a bit more leeway is given with a 0.05 limit. At 0.08, then, the U.S. has set the legal limit higher than most, even if others, including the UK, Canada, Ireland, and New Zealand, share the same standard. Unfortunately, this may be an ineffective measure for preventing car accidents in more ways than one, as many drivers do not bother to comply with this legal guideline.

In 2010, the Centers for Disease Control and Prevention reported that roughly 1.8 percent of all respondents to its Behavioral Risk Factor Surveillance System survey admitted to one or more episodes of alcohol-impaired driving in the past 30 days. Based on this data, researchers estimated that throughout the year, four million people drove while impaired, and this amounted to nearly 112 million distinct episodes of drunk driving. Another study of randomly stopped nighttime drivers at 300 locations across 48 states found that over one in ten drivers had some alcohol in their systems, while nearly one in 20 drivers had a BAC of 0.05 or higher. Apparently, drunk driving is disproportionately high among binge drinkers, young men, and people who do not regularly wear seat belts.

Because of the increased risk of crashes due to drunk drivers, many people support alcohol ignition interlocks, equipment connected to the ignition circuit that prevents the engine from starting until a breath sample has been provided, analyzed, and determined to be below the legal limit. According to the AAA Foundation for Traffic Safety, about 53 percent of respondents strongly favor laws requiring all drivers convicted of DWI to have an interlock installed, even on a first conviction, 28 percent somewhat favor those laws, while a full 71 percent of respondents supported a requirement that all new cars have built-in technology preventing a vehicle from starting if the driver’s alcohol level is over the legal limit. Until such laws are passed, though, researchers continue to monitor driving accidents and their relationship to drinking.

Official Blame for Crashes

Based on the fact that laboratory studies found some driving impairment at a BAC of 0.01, a team of researchers decided to investigate whether official blame for a crash increases significantly at that minimally buzzed level outside in the real world, beyond the laboratory. The team analyzed records from the U.S. Fatality Analysis Reporting System, an official, nationwide database, between the years 1994 and 2011. In particular, the researchers looked for the driver’s BAC and the degree to which he or she was assigned sole official blame (SOB) for any crash. What did they discover?

Even minimally buzzed drivers are 46 percent (24 to 72 percent) more likely to be officially blamed for a crash than their sober crashees. In fact, they found no line of demarcation, whereby drivers went from blameless to blamed, at the legal limit of 0.08 BAC. Instead, SOB increases smoothly and strongly with a near-linear SOB-to-BAC relationship beginning at 0.01 BAC and ending around 0.24 BAC. “U.S. legislators should reduce the legal BAC limit, perhaps to 0.05 percent, as in most European countries,” wrote the authors.

Source: Phillips DP, Sousa ALR, Moshfegh RT. Official blame for drivers with very low blood alcohol content: there is no safe combination of drinking and driving. Inj Prev. 2014.