The Grapevine

Not-So-Good Vibrations? How Your Car Could Be Making You Sleepy

Some of the reasons why we feel drowsy while driving may involve hangovers, using medications that make you sleepy, working night shifts, etc. But what happens when the cause happens to be our mode of transport?

The study titled "The Effects of Physical Vibration on Heart Rate Variability as a Measure of Drowsiness" was published in the journal Ergonomics.

It's not news that vibrating sensations can feel very relaxing — they're an integral feature of robotic massage chairs after all. But the effects of the physical vibrations we feel while traveling in a vehicle have not been understood well enough, according to professor Stephen Robinson.

"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 Robinson who is from the department of psychology at RMIT University, Australia. "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."

The cross-disciplinary research team recruited 15 people for the study, asking them to use a driving simulator which was developed at RMIT. It was set up on a platform, designed in a way that mimicked the experience of driving on a monotonous two-lane highway. 

The participants used the driving simulator two times. Once when the vibrations were at low frequencies (4 - 7Hz) and once when no vibrations were used. During the process, the research team measured the heart rate variability of the participants.

The sleepiness kicked in a mere 15 minutes after entering the vehicle. It began to affect concentration after 30 minutes, taking substantial effort for the participants stay alert. Their drowsiness seemed to progressively increase as the test continued, peaking at 60 minutes. 

"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 Mohammad Fard from the school of engineering at RMIT.

The Centers for Disease Control and Prevention notes drowsy driving is a major problem in the United States, being a potential cause for thousands of fatal crashes every year. One of their studies revealed 1 in 25 adult drivers fell asleep at the wheel at some point over the previous 30 days.

By conducting further research, both larger and more diverse, the team hoped to examine how vibrations could affect various demographics differently. 

Moreover, not all vibrations on the road are bad according to the researchers. The findings suggested vibrations at certain frequencies could actually have an opposite effect and keep people awake and alert.

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

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