Drugs, alcohol contribute to fatal accidents - but how much?

When we read or hear about fatal traffic accidents, it's not uncommon or surprising to learn that alcohol or drugs were involved. A new study on alcohol and drug use among drivers killed in crashes offers some startling statistics that remind us of the very real danger of driving while intoxicated. But it also indicates that we have much more to learn about the effects of combining some of those intoxicants, even in small amounts.

The study's central finding was that among U.S. drivers who were killed in car accidents, more than half had drugs or alcohol in their system at the time of the crash. It also determined that male and nighttime drivers killed in crashes were most likely to have drugs or alcohol appear on a toxicology screen.

The study used National Highway Traffic Safety Administration data on fatal accidents in 14 states from the years 2005 to 2009. Of the more than 20,000 drivers who died, 57 percent tested for at least one drug, including alcohol. About one out of every five drivers had multiple drugs appear on their toxicology screens, with alcohol being the most common. Less than 50 percent of women killed in crashes had alcohol or drugs in their system, while 60 percent of men tested positive for these substances. When it came to race, blacks and whites had the same likelihood of testing positive, while Asians were significantly less likely and Native Americans much more likely.

What the study couldn't determine was whether the substances that appeared on a tox screen were enough to impair the drivers. It also didn't specify whether the prescription drugs were abused or used correctly, or whether their combination caused a significant driving impairment. Even the effects of illegal drugs such as marijuana couldn't be measured accurately, because they can continue to stay in a driver's system long after the intoxicating effects have passed.

In other words, we know that many drivers killed in accidents previously consumed drugs and alcohol, but we don't know to what extent those substances contributed to their death. Alcohol impairment is much easier to measure than the effects of one or more other drugs, and we have a lot more to learn about how these drugs contribute to fatal accidents. But it's still safe to say that being impaired behind the wheel is a great risk not just to drivers themselves, but their passengers, other drivers and anyone else in their path.

Source: CNBC, "Alcohol, drugs common in fatal crashes," Sept. 6, 2012

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