The number of people driving under the influence of alcohol on U.S. roads continues to decline, but the number of drivers using marijuana and prescription drugs that can affect road safety is climbing, according to two studies released by the Department of Transportation's National Highway Traffic Safety Administration.
One study found that the number of inebriated drivers has declined by nearly one-third since 2007, but that same survey found a large increase in the number of drivers using marijuana or other illegal drugs. In the 2014 survey, nearly one in four drivers tested positive for at least one drug that could affect safety.
"The latest Roadside Survey raises significant questions about drug use and highway safety. The rising prevalence of marijuana and other drugs is a challenge to everyone who is dedicated to saving lives and reducing crashes," said NHTSA Administrator Mark Rosekind.
The latest edition of the survey shows that about 8% of drivers during weekend nighttime hours were found to have alcohol in their system, and just over 1% were found with 0.08% or higher breath alcohol content - the legal limit in every state. This is a marked reduction of about 30% from the previous survey in 2007 and 80% from the first survey in 1973.
At the same time, the number of weekend nighttime drivers with evidence of drugs in their system rose from 16.3% in 2007 to 20% in 2014. The number of drivers with marijuana in their system grew by nearly 50%.
A second survey was conducted to determine whether marijuana use increases the risk of crashes. It found that marijuana users are more likely to be involved in accidents, due in part because they are more likely to be in groups at higher risk of crashes such as young men.
"Drivers should never get behind the wheel impaired, and we know that marijuana impairs judgment, reaction times and awareness," said Jeff Michael, NHTSA's associate administrator for research and program development. "These findings highlight the importance of research to better understand how marijuana use affects drivers so states and communities can craft the best safety policies."
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