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The case for .08 BAC: science vs. myth


Date: Friday, 27. August 2010

When automotive journalist Eric Peters argues that at a BAC of .08 or less there is little enough alcohol in a driver's system that it is "extremely unlikely to appreciably affect coordination, reaction times, vision, or judgment in a normal person," he is contradicting science ( NHTSA fact sheet ).

"He's wrong," says Dr. Robert Mann, a senior researcher with the Toronto-based Addiction Research Foundation. "There's substantial evidence that there's impairment at levels as low as .02." Dr. Mann concedes that Peters is right in pointing out that the bulk of the drinking and driving problem is due to BACs over .10. However, Mann points out, studies of BAC levels and crash risk, including the landmark Grand Rapids study back in the '60s, show the risk of crashing increasing significantly at levels below .04 and then rising sharply as BAC passes .05. By the time it gets to .10 the risk graph has become more vertical than horizontal.

A study by the Traffic Injury Research Foundation found that, at BAC levels of .05 to .08, the risk of collision for drivers in the 20+ age group was about twice that of drivers with zero BAC. For young novice drivers (16- to 19 years of age) the crash risk at .05 to .08 was about eight times that of normal drivers!

A 1994 research document released by the National Highway Traffic Safety Administration also identifies impairment problems at .02 and states that "virtually all drivers are substantially impaired at .08 BAC.

Peters: impairment is subjective asked Peters how he regards the overwhelming scientific evidence on impairment at lower BAC levels. "Impairment," he responded, "is an extremely subjective term; one could equally argue that anyone over 60 is "impaired" vis-a-vis a healthy 25 year old, in terms of visual acuity, reaction times, etc." And what about handicapped drivers? he adds? Couldn't one also argue they are impaired as compared to a person with full use of all their limbs & faculties?

He makes an interesting point. Drivers vary enormously in their abilities. A healthy and highly competent driver might argue that he or she is more capable than the average driver, even when impaired by alcohol, and certainly when only slightly impaired at lower BAC levels. Peters says, "While a person with a small amount of alcohol in their system may be said to have a slight reduction in performance/reaction times/visual acuity, etc., they are not DRUNK ...and categorizing them as such-especially when they've done nothing to indicate impairment but instead have had the misfortunate to run into a 'sobriety checkpoint'-is unjust, poor public policy and arguably vicious."

Alertness, judgment first to go

Peters's argument implies that he seriously misunderstands impairment and driving, particularly alcohol impairment. Drivers who have impairments due to age, loss of limbs, or other such disabilities, deal with these on an ongoing basis. They learn to adapt and manage their skills and their exposure to risk.

They are not cognitively impaired, points out Rick Cerna, Secretary of the American Association of Driver Educators for the Disabled. Their ability to reason and make judgments is usually not affected, he says, and if it is (for example in the case of brain injuries) they are normally subjected to a screening process that includes input from members of their family, physicians, and friends before they are allowed to drive.

Margaret Young, operator of a driver rehabilitation center in Toronto, says her clients are not high risk drivers. Research by the Ontario Ministry of Transportation and the Society of Automotive Engineers, she points out, shows no significant difference in crash rates between rehabilitated drivers and the general driving population.

This is very different from alcohol impaired drivers at .08 BAC, who crash at a much higher rate than drivers who have not taken alcohol and typically do not feel impaired. In fact, they are likely to feel better about their driving after taking a few drinks. The most difficult disability to deal with is the one you don't realize you have, says Cerna.

A problem with setting legal BAC near limits at which impairment becomes visible is that it tends to send a wrong message to drivers that there is no impairment at lower levels. A few drinks becomes OK.

Drivers tend to be seduced by their success in drinking alcohol and driving. When they make it home they may feel they've demonstrated their capability. And if they read about an alcohol-related crash in the newspaper the following morning, as one researcher pointed out, they may even see this as confirmation of their individual abilities rather than as a warning.

A final argument for lower BAC limits is the potential for a low level of blood alcohol to combine with another impairment to produce a multiplier effect. For example, recent research indicates that in a fatigued driver a BAC of .05 could have the same impairment effect as .10 or more in a non-fatigued driver.

All things considered, there really isn't much to support arguments against lowering BAC limits from .10 to .08. It isn't much of a burden on lifestyles. It promotes respect for alcohol, and the lives saved will be a huge benefit, both in social costs avoided and family members who will not be missing because of some tragedy on the roads.

Read a response to this editorial by Eric Peters.

Further comments to this article have been disabled.

All Comments (3)

Showing 1 - 3 comments

geoffery gotche,

and thank you jason!

geoffry gotche,

you wasted my time


Let me first say this, 93% of all accidents are non-alcohol related. Of the remaining 7%, not all of these are were caused by the person who may have had a drink. Lowering the BAC to .08 is nothing more than government getting more money out of individuals who buy alcohol. .08 BAC is absolutley insane!! Im all for keeping drunks off the road, but this has gone way too far. If a guy drinks 3 beers after work, just hanging out with a few buddies for an hour, and drives home, he will face blowing .08. Lets see, would i wanna ride with him or the 80 year old lady down the street who cant see beyond her car hood...what a joke.

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