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Research: Driving crash risk jumps at 0.01 blood alcohol concentration

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Drivers who drink alcohol, but not enough to reach the legal threshold of 0.08 blood alcohol concentration (BAC), are still more likely to cause traffic collisions than those who are sober, according to a University of California San Diego study. The research published in January's Injury Prevention, examined crash data in what is being considered the first nationwide research on actual fatal and non-fatal car crashes caused by minimally buzzed drivers.

UCSD sociologist David Phillips and his team found drivers with a BAC of 0.01 percent are 46 percent more likely than a sober driver to be officially and solely blamed by accident investigators for causing a collision. They found that blame increases steadily and smoothly from 0.01 (a single drink) to 0.24 (three times the legal limit).

"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," Phillips said. "Our data support both the National Highway Traffic Safety Administration's (NHTSA) campaign that 'buzzed driving is drunk driving' and the recommendation made by the National Transportation Safety Board (NTSB) to reduce the legal limit to BAC 0.05 percent. In fact, our data provide support for yet greater reductions in the legal (BAC)."

Phillips said police and judges -- along with the public at large -- treat 0.08 as "a sharp, definitive, meaningful boundary," and authorities don't impose severe penalties on those below that standard. "The law should reflect what official accident investigators are seeing," Phillips said.

During the entire year, an average of 25 people are killed each day by intoxicated motorists according to data from the NHTSA. One out of every 10 arrests for all crimes in the U.S. were for Operating While Impaired (OWI) – above the 0.08 standard – accounting for one out of every 80 licensed drivers.

Earlier lab studies find reaction time to be 1/5 of a second for an unimpaired driver. A heavy drinker or one with the disease of alcoholism may not "feel" impaired at minimally buzzed BACs, but the lab shows a definite deterioration of reaction time. With alcohol in the system, reaction time is slowed to 4/5 of a second at 0.06 BAC. At 60 mph, a second means 88 feet. A fifth of a second is 17.5 feet, 4/5 of a second is 70.4 feet. The car slamming on the brakes in front of an impaired driver is 53 feet closer, reaction-time wise, compared to an unimpaired driver.

Yet another study indicated at 0.02 to 0.05 BAC, the ability to see or locate moving lights correctly is reduced as is reaction time and the ability to judge distance. Even if not obviously impaired, at 0.05 BAC drivers are twice as likely to have a crash as before they started drinking...At 0.08 BAC drivers are five times more likely to have a crash than before they started drinking. Over 0.08, the crash likelihood jumps to 10 times that of a sober driver. The increase bears out in the new UCSD study of actual crashes as well.

A May 2013 hearing by the NTSB produced ideas for reducing drinking and driving deaths, among the ideas, lowering the limit legal for driving from 0.08 to 0.05 BAC. One hundred other countries have lower BAC limits for driving than the U.S. The idea is being debated around the country because the board has no authority to make the recommendation a law.

The last time the NTSB recommended a blood alcohol limit change, from 0.10 to 0.08, it took two decades and the threat of Congress withholding highway funds for the idea to become law in all 50 states. An Indiana state legislator, Senator Michael Crider, R-Greenfield, predicts that is what it will take again. "If you look at the percentile drops, it's a pretty significant drop in the legal driving limit for drunk driving. It's going to be something not necessarily real popular, based on what I saw last time."

Mothers Against Drunk Driving (MADD), an expected ally of the proposed lower limit, is not behind it, instead focusing on its own three-pronged agenda for reducing impaired driving. The NHTSA also opposes the change to 0.05. Republican leaders on Capitol Hill say, "Leave it to the states to decide."

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