Drunk Driving Is Declining … While Drugged Driving Accelerates

People driving under the influence of drugs are playing an increasing role in crashes.

For decades, public service announcements have warned Americans against drinking alcohol and driving. Media reports have graphically shown the deadly consequences of alcohol-caused wrecks. Coupled with stiff penalties for driving while intoxicated, the long running campaign to stop drunk driving in the U.S. has made roads safer.

But while fewer drivers are hitting the road drunk, more are heading down the highway on drugs, according to research by the Department of Transportation’s National Highway Traffic Safety Administration (NHTSA).

Conducted five times over the past four decades, the NHTSA’s National Roadside Survey of Alcohol and Drug Use by Drivers consists of data from drivers across the nation who are alerted by roadside signs that a voluntary survey site is ahead. Information collected, including breath alcohol content, is anonymous. The latest survey found about 8 percent of drivers during weekend nighttime hours had alcohol in their system and just over 1 percent had breath alcohol content over the legal limit in every state.

The survey results had good news. The number of drivers with alcohol in their system has plummeted by one-third since 2007, and by more than three-quarters since the first NHTSA survey was conducted over 40 years ago. However, alcohol isn’t the only mind-clouding and reflex-slowing drug that can make driving dangerous — the research revealed marijuana and other drug use by drivers has increased substantially, raising red flags about highway safety.

In 2007, the number of weekend nighttime drivers with drugs in their system was 16.3 percent. Seven years later, the number had climbed to 20 percent. Overall, nearly one in four drivers tested positive for at least one illegal, prescription or over-the-counter drug that can impact the ability to drive safely.

Fifty percent more drivers were found to have marijuana in their system, compared to the last survey. But does using that drug make driving dangerous?

To answer that question, the NHTSA conducted another survey using data from more than 3,000 drivers who were involved in crashes over a 20-month period and a comparison group of 6,000 drivers who had not been involved in accidents. The results showed those who had used marijuana were more likely to be involved in crashes than drug-free drivers. However, the findings could be explained, the report noted, by the fact that marijuana users are more likely to be young men who are already at a higher risk for car crashes.

However, research so far with driving simulators has revealed that marijuana at high enough levels in the body does affect a driver’s ability to drive safely. The NHTSA plans a series of additional studies to learn more about the risk of drugged driving. To get the word out that smoking pot and driving could be dangerous, the NHTSA has launched a “Buzzed Driving is Drunk Driving” campaign, too.

“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.”

Researchers at Columbia University's Mailman School of Public Health examined toxicological testing data from the NHTSA Administration's Fatality Analysis Reporting System to look for a link between fatal crashes involving drivers and non-alcohol drugs. In a study of 23,591 drivers who died within 1 hour of a crash, almost 40 percent tested positive for alcohol and almost 25 percent tested positive for other drugs. Marijuana was the most commonly detected non-alcohol drug, suggesting it could play a role in the increasing number of fatal motor vehicle crashes involving drug-using drivers.

"Although earlier research showed that drug use is associated with impaired driving performance and increased crash risk, trends in narcotic involvement in driver fatalities have been understudied," said Guohua Li, MD, DrPH, professor of Epidemiology and Anesthesiology and director of Columbia University’s Center for Injury Epidemiology and Prevention. "Given the increasing availability of marijuana and the ongoing opioid overdose epidemic, understanding the role of controlled substances in motor vehicle crashes is of significant public health importance."