Car Vibrations Could Cause Drivers to Feel Sleepy at the Wheel

Vibrations caused by a running car engine can lull drivers into a sleepier state within minutes of hitting the road, according to a study.

Drowsy driving is a major problem in the U.S. according to the Centers for Disease Control and Prevention, with an estimated one in 25 drivers over the age of 18 having fallen asleep at the wheel in the past 30 days. Drowsy driving resulted in more than 72,000 crashes, 44,000 injuries and 800 deaths in 2013. But experts fear the number of fatal crashes could be as high as 6,000.

Researchers based at RMIT University, Australia, sought to uncover why drivers risk dozing off at the wheel in the hope of preventing this behavior and cutting the number of accidents.

"When you're tired, it doesn't take much to start nodding off and we've found that the gentle vibrations made by car seats as you drive can lull your brain and body," Stephen Robinson, author of the study and professor of psychology at RMIT University, said in a statement.

When a vehicle like a car or truck is running, it emits steady vibrations at low frequencies, according to the authors of the study published in the journal Ergonomics.

These tiny movements can make even those who are well-rested and healthy feel sleepy, the researchers believe.

To arrive at their theory, researchers recruited 15 volunteers. They were asked to sit in a virtual simulator that recreated the experience of driving on a monotonous, two-lane highway.

In two tests, the participants were exposed to low frequencies and no vibrations, respectively. Their heart rate was measured throughout the hour-long test.

The researchers found the vibrations made the participants feel tired. This in turn made it harder for them to perform mental tasks. The nervous system responded by changing the individual's heart rate.

After 15 minutes of vibration, the volunteers showed signs of drowsiness. And after 30 minutes, they were significantly drowsy and had to try hard to stay alert and process their surroundings. Their drowsiness reached its peak after 60 minutes.

Interestingly, the research also suggested vibrations at different frequencies could have the opposite effect and help keep people awake, explained Dr. Mohammad Fard, associated professor at the RMIT school of engineering.

"So we also want to examine a wider range of frequencies, to inform car designs that could potentially harness those 'good vibrations,'" he said.

Before that can happen, a further study involving a larger group of participants is needed to investigate how factors such as age could make someone more vulnerable to vibration-induced drowsiness. The impact of health problems such as sleep apnea are also an important line of inquiry, said Fard.

Robinson told Newsweek: "If a driver becomes aware that they are becoming drowsy and losing concentration, the safest course of action is to pull over and change drivers or take a power nap."

This article has been updated with comment from professor Stephen Robinson.

Correction: This article previously stated the research was conducted at the University of Melbourne. It has since been updated to state the research was carried out at RMIT University.