Fatigue reduces a driver's alertness, concentration and reaction time.
One in five of all crashes on major roads are caused by tired drivers, and sleep-related collisions are more likely than others to result in a fatality or serious injury.
New research shows that vibrations in cars make people sleepier, affecting concentration and alertness levels just 15 minutes after drivers get behind the wheel.
"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," said Professor Stephen Robinson from Australia's RMIT University, one of the authors of a paper published in the journal Ergonomics.
The research team tested 15 volunteers in a virtual simulator that replicates the experience of driving on a monotonous two-lane highway. They found that within 15 minutes of starting the 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.
"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," Professor Robinson explained.
"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."
The researchers hope their findings can be used by manufacturers to improve car seat designs, incorporating features that disrupt this effect and fight vibration-induced sleepiness.
How do you fend off sleepiness behind the wheel?