Why Do You Get Sleepy When You Drive？
Most of us have probably felt sleepy on a car journey, but it's not always due to an early start, or a long day, or a lack of caffeine.
It's all to do with the vibrations a car makes as it moves: they can bring on sleepiness in just 15 minutes, the new study shows. That's something for both car manufacturers and road safety experts to think about, according to the researchers from RMIT University in Australia. They want to conduct further studies into how car seat vibrations could be secretly bringing on sleep.
"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," says one of the team, 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."
Robinson and his colleagues hooked 15 volunteers up to a virtual simulator that they could vibrate at different frequencies. The volunteers were tested twice, once with no vibration, and once with low-frequency 4-7 Hz vibrations. They then measured the heart rate variability (HRV) of the participants.
These researchers discovered that levels of alertness after driving for only 15 min begin to decrease dramatically, and by 30 minutes will have a significant impact on your ability to stay alert and concentrate on the road. By 60 minutes sleepiness was at its peak. However, with tiredness a factor in around 1 in 5 fatal accidents on the road, it's important to make further studies. The researchers want to continue their work by looking at bigger groups of people and more ranges of frequencies.
This is the first study to investigate the effects of whole-body vibration on seated human alertness and drowsiness. The data clearly demonstrate that exposure to vibration has considerable influence on subjective sleepiness levels, and more importantly, human reaction times and lapses of attention.
These findings need to be further consolidated particularly in relation to driving behavior. This line of research can then assist in the development of practical and relevant guidelines for limitation of vibration exposure in the automotive industry, in an effort to reduce the burden of road accidents.
1. vibration n. 震动；颤动；抖动；（感情的）共鸣
2. nod off 打盹
3. lull v. 使放松；使镇静
4. heart rate variability 心率变异性
5. drowsiness n. 睡意；困倦；假寐
6. lapse n. (一时的) 走神; 判断错误