Drexel Study: Are You Really OK to Drive Right Now?

Driving Photo
(Photo credit: Tony Webster / flickr)

While anyone who has taken a high school health class knows the perils associated with drinking and driving, other factors that contribute to motor vehicle accidents — like marijuana, fatigue and texting — are more easily overlooked.

The increased risk of driving errors due to physiological impairments or distractions is a growing public health concern, says a new paper from Drexel University researchers.

“There has been such a good job getting the message across about the dangers of drinking and driving that it has actually gone down. At the same time, driving and drug use has gone up,” said lead author David Vearrier, MD, an assistant professor in the College of Medicine and emergency medicine physician. “Maybe we are missing the boat on informing patients that driving while using drugs can be just as dangerous.”

The paper, published in this month’s issue of “Disease-a-Month” and designed primarily as a guide for primary care physicians, is one of the largest and most comprehensive reviews of driving impairment to date. Vearrier and his colleagues analyzed nearly 300 peer-reviewed articles and other documents to determine the scope of the problem.

Some highlights:

  • Marijuana is the most common drug of abuse reported in connection with impaired driving and motor vehicle crashes.
  • Marijuana prevalence in fatal U.S. motor vehicle crashes tripled from 4.2 percent in 1999 to 12.2 percent in 2010, according to an analysis of the Fatality Analysis Reporting System (FARS), a census of fatal U.S. motor vehicle crashes.
  • Among a group of regular ecstasy users, half reported driving under the influence in the past six months, and more than half believed their driving was unchanged or improved under the influence.
  • In one simulation study, drivers who rated themselves as likely to fall asleep in the next few minutes, were four times more likely to have a subsequent driving accident.
  • Several studies have reported that consumption of caffeine improves driving performance in fatigued drivers. In one driving simulation study, consumption of an energy drink that contained 160 mg of caffeine at the beginning of a 150-minute drive was associated with decreased SDLP (the standard deviation of lateral position) and steering wheel deviations during the first 100 minutes of the drive.
  • In the United States in 2013, 16 percent of all police-reported motor vehicle accidents were caused by a distracted driver. 3,154 people were killed and 424,000 were injured by distracted drivers during this year, though the study authors note these numbers are probably much larger, since drivers often do not report distracted behaviors.
  • Many attribute the increase in distracted driving fatalities to an increase in mobile phone use. After declining from 1999 to 2005, fatalities related to distracted driving increased by 28 percent from 2005 to 2008. During this time, cell phone subscriptions and text-messaging volumes also increased.
  • Texting while driving increased dramatically from 2002 to 2007, resulting in an estimated 16,141 additional fatalities during this time.
  • Eating while driving has been reported to be similar to texting in its effects on driving performance.

Some of the paper’s conclusions might seem like a no-brainer. But Vearrier said he was surprised by the number of studies showing how many people do not realize they are impaired while on the road.

With a number of states decriminalizing medical and recreational marijuana, for example, he worries that too many drivers believe they are OK to drive when they are high.

“The big takeaway is that driving is a very complex task, and it requires a lot of complex human behaviors and abilities,” Vearrier said. “There are so many different skills that go into it, and all types of behaviors that can derail our ability to prevent crashes.”

For media inquiries, contact Lauren Ingeno: lingeno@drexel.edu or 215-895-2614.

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