How Vibrations in Cars Make Drivers Sleepy

Summary: A new study reveals the natural vibrations of cars make people feel sleepier. After just 15 minutes of driving, concentration and alertness levels are reduced for those behind the wheel.

Source: RMIT University.

New research has found the natural vibrations of cars make people sleepier, affecting concentration and alertness levels just 15 minutes after drivers get behind the wheel.

With about 20 per cent of fatal road crashes involving driver fatigue, researchers from RMIT University in Melbourne, Australia, hope their findings can be used by manufacturers to improve car seat designs to help keep drivers awake.

Professor Stephen Robinson said the effects of physical vibration on drivers were not well understood, despite growing evidence that vibration contributes to feelings of sleepiness.

“We know 1 in 5 Australians have fallen asleep at the wheel and we know that drowsy driving is a significant issue for road safety,” Robinson said.

“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.

“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.

“From 15 minutes of getting in the car, drowsiness has already begun to take hold. In half an hour, it’s making a significant impact on your ability to stay concentrated and alert.

“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.”

Led by chief investigators Associate Professor Mohammad Fard and Professor Stephen Robinson, the research team tested 15 volunteers in a virtual simulator that replicates the experience of driving on a monotonous two-lane highway.

The simulator was set up on a platform that could be vibrated on different frequencies, with the volunteers tested twice – once with vibrations at low frequencies (4-7Hz) and once with no vibration.

The tiredness induced by vibration makes it psychologically and physiologically harder to perform mental tasks, so the body’s nervous system activates to compensate, leading to changes in the heartbeat.

a simulation of a car driving
Volunteers were tested on a virtual simulator that can be vibrated on different frequencies. image is credited to RMIT University.

By looking at the volunteers’ heart rate variability (HRV), researchers were able to gain an objective measure of how drowsy they were feeling as the 60-minute test progressed.

Within 15 minutes of starting the vibrating test, volunteers were showing signs of drowsiness. Within 30 minutes, the drowsiness was significant, requiring substantial effort to maintain alertness and cognitive performance.

The drowsiness increased progressively over the test, peaking at 60 minutes.

Associate Professor Mohammad Fard said more work was needed to build on the findings and examine how vibrations affected people across different demographics.

“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,” he said.

“Our research also suggests that vibrations at some frequencies may have the opposite effect and help keep people awake.

“So we also want to examine a wider range of frequencies, to inform car designs that could potentially harness those ‘good vibrations’.”

About this neuroscience research article

Source: Gosia Kaszubska – RMIT University
Publisher: Organized by
Image Source: image is credited to RMIT University.
Video Source: Video credited to RMIT University.
Original Research: Abstract for “The Effects of Physical Vibration on Heart Rate Variability as a Measure of Drowsiness” by N. Zhang, M. Fard, M.H.U. Bhuiyan, D. Verhagen, M. F. Azari & S. R. Robinson in Ergonomics. Published June 6 2018.

Cite This Article

[cbtabs][cbtab title=”MLA”]RMIT University”How Vibrations in Cars Make Drivers Sleepy.” NeuroscienceNews. NeuroscienceNews, 5 July 2018.
<>.[/cbtab][cbtab title=”APA”]RMIT University(2018, July 5). How Vibrations in Cars Make Drivers Sleepy. NeuroscienceNews. Retrieved July 5, 2018 from[/cbtab][cbtab title=”Chicago”]RMIT University”How Vibrations in Cars Make Drivers Sleepy.” (accessed July 5, 2018).[/cbtab][/cbtabs]


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We investigated the effects of low frequency whole body vibration on heart rate variability (HRV), a measure of autonomic nervous system activation that differentiates between stress and drowsiness. Fifteen participants underwent two simulated driving tasks for 60 minutes each: one involved whole-body 4-7 Hz vibration delivered through the car seat, and one involved no vibration. The Karolinska Sleepiness Scale, a subjective measure of drowsiness, demonstrated a significant increase in drowsiness during the task. Within 15-30 minutes of exposure to vibration, autonomic (sympathetic) activity increased (p < 0.01) in response to the stress of maintaining alertness and performance when drowsy, and peaked at 60 minutes (p < 0.001). Changes in three other HRV domains (higher LF/HF ratios, lower RMSSD (ms), and pNN50 (%) values) were consistent with increased sympathetic activation. These findings have implications for the future development of equivalent drowsiness contours leading to improvements in road safety.

Practitioner Summary: The effects of physical vibration on driver drowsiness have not been well investigated. This laboratory-controlled study found characteristic changes in heart rate variability (HRV) domains that indicated progressively increasing neurological effort in maintaining alertness in response to low frequency vibration, which became significant within 30 minutes.

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