Researchers in Australia have found that an automobile’s natural vibrations can make drivers sleepy, increasing the risk of what is called “drowsy driving.”

A 2015 report by the National Highway Traffic Safety Administration found, in the United States alone, that drowsy driving was responsible for 72,000 police-reported crashes.

From these accidents, 41,000 people were injured and more than 800 died.

The NHTSA report goes on to state that among those involved with traffic safety, sleep science, and public health there is a broad consensus that this is an underestimate of the actual impact of drowsy driving.

Volunteers were tested on a virtual simulator that can be vibrated on different frequencies. (RMIT University)

In a new study, researchers from RMIT University, in Melbourne, Australia, detail evidence that normal automobile vibrations at frequencies between 4 and 7 hertz can affect a driver’s concentration and alertness levels a mere 15 minutes after getting behind the wheel.

“Our study shows steady vibrations at low frequencies – the kind we experience when driving cars and trucks – progressively induce sleepiness even among people who are well rested and healthy, said RMIT professor Stephen Robinson, who is one of the two chief study investigators, in a university press release.

The researchers made their findings after testing 15 volunteers in a virtual simulation of driving on a boring two-lane highway.

The volunteers were first put through the driving simulation with low-frequency vibrations and then with no vibrations.

The researchers found that the vibration induced feeling of tiredness makes performing mental tasks harder to perform both psychologically and physiologically.

To compensate for this they say the body’s nervous system becomes stimulated, which, in turn, can cause the heart’s average beats per minute to vary.

The study's Chief Investigators, Professor Stephen Robinson and Associate Professor Mohammad Fard. (RMIT University)

The study’s Chief Investigators, Professor Stephen Robinson and Associate Professor Mohammad Fard. (RMIT University)

The study authors say they were able to make an objective measurement of just how drowsy the volunteers were by examining changes to their heart rate variability (HRV) throughout the one hour test.

“To improve road safety, we hope that future car seat designs can build in features that disrupt this lulling effect and fight vibration-induced sleepiness,” said Professor Robinson.

The researchers say that since more work is needed to expand on their findings, they would like to continue their investigation.

“We want to study a larger cohort, particularly to investigate how age may affect someone’s vulnerability to vibration-induced drowsiness as well as the impact of health problems such as sleep apnea,” said the study’s other chief research investigator Mohammad Fard, an Associate professor at RMIT University.

Fard said they’d like to conduct the future tests with vibrations that span across a wider frequency range.

The study outlining the researcher’s findings has been published in the journal Ergonomics.

How Vibrations In Cars Make Drivers Sleepy | RMIT University