我怎么又在地铁上睡着了……

不翻来覆去1小时、换上50个睡姿，是绝对不可能入睡的。

不过地铁公交上，要睡着却很简单。乘客的低语混杂着发动机的嗡鸣像是天然的白噪音，摇晃的车体又类似婴儿的摇篮，开车不一会儿，车上的人就东倒西歪的了。

 在交通工具上更容易入睡，这是真的吗？

网友PrionBacon评论认为，车上比床上更困倦是因为感觉输入在一段时间里是稳定重复的。

Much like a smartphone, your body will go to sleep when there are no new inputs.

其实就跟智能手机挺像的，身体没有新的外界输入的时候就会休眠。

When you are on a bus, your senses will give you the same repetitive inputs. The streets will flow by, the AC and engine adds constant white noise, you're seated and not moving, and the smell... well you hope the smell doesn't change.

坐公交的时候，你感知到的输入一直是重复的。街道飞驰而过，空调和引擎发出的白噪声，你坐着且并没有动，还有车上的味道……呃，你希望车上的味道最好不要变。

Any repetitive input going to your brain will eventually be ignored and your brain will start going into a low energy state. The fact that you fall asleep quickly when closing your eyes on a bus is because you were already on the bus for a while and got used to all the repetitive sensory data.

你的大脑最终会忽略这些重复性的输入，然后进入低耗能模式。你在公交上闭着眼睛就能睡着就是因为你其实坐上公交已经好一会儿了，早就习惯了所有重复的感知数据。

When you go to bed, you have a lot of new changes. You are lying down, you wear different clothes, you feel the pressure of your covers, you go from bright to dark, noisy to quiet. All of these arenew sensory inputs that your brain needs to get used to before going to sleep.

但是爬上床睡觉的时候，你会经历许多感知变化。你躺倒了，换了睡衣，被子有重量，关了灯，静了音。所有这些新的感知输入都会需要你的大脑花时间来适应才能睡着。

 科学家们的解释可能更为严谨：交通工具上的瞌睡可能是振动造成的。

发表在美国职业安全与健康研究院杂志《工业健康》（Industrial Health）上的一项研究对交通工具使用者瞌睡受振动的影响进行了调查。

研究者在实验中设置了一个汽车座位，并在座位底下安装了振动平台。参与实验的志愿者们将会经受频率在1-15赫兹之间的正态分布随机振动，持续20分钟。

研究者发现，18位志愿者在警觉度测试与瞌睡度评估方面都出现了显著变化。

这表明，哪怕是只暴露在20分钟的振动下，志愿者的运动神经表现都会受到较强的瞌睡影响。

This is, to our knowledge, the first study to investigate the effects of whole-body vibration on seated human alertness and drowsiness. Our data clearly demonstrate that exposure to vibration has considerable influence on subjective sleepiness levels, and more importantly, human reaction times and lapses of attention.

据我们所知，这是第一个以全身振动对坐着的人的警觉性和睡意的影响为对象的研究。我们的数据清楚地表明，振动对主观嗜睡水平有很大的影响，更重要的是，对人类的反应时间和注意力缺失也有显著影响。

These findings need to be further consolidated particularly in relation to driving behavior (steering entropy). 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.

这些研究结果需要得到进一步的完善，特别是在与驾驶行为（转向熵）相关的方面（要做进一步调查）。这类研究将帮助制定实用的相关指南，指导汽车制造业限制振动暴露，以达到减少道路事故的目的。

 此外，来自RMIT University的研究者们也做了类似的实验，他们表示：

What might be happening is that the brain becomes synchronized to the vibrations and enters an early stage of sleep –hence, why you might get a whole car full of people nodding off on a long trip.

事实上（在交通工具上）大脑与振动同步并进入了早期的睡眠状态——这也就是为什么长途汽车上的乘客总是东倒西歪地“钓鱼”了。

That's something for both car manufacturers and road safety experts to think about.

该发现需要得到汽车制造商与道路安全专家的注意。

很多人觉得是“车上睡得香”导致了“晚上睡不着”。怎样才能毫不费力地掰正你的生物钟呢？

Carve out at least 30 minutes of wind-downtime before bed in which you do something relaxing, such as read a book. Dim the lights in the house slightly for an hour or so before bed.

睡前至少留出30分钟的休息时间，做些放松的事情，比如看书。睡觉前把屋里的灯稍微调暗一个小时左右。

Disconnect from close-range electronic devices such as laptops, phones, and tablets, as the light from their screens can alert the brain and make it harder to fall asleep.

与笔记本电脑、手机、平板电脑等近距离电子设备断连，因为屏幕上的光线会让大脑清醒，让你难以入睡。

 To calm your mind, do a breathing or relaxation exercise.

为了平心静气，你可以做点呼吸放松训练。

If you get into bed and cannot fall asleep after 20 minutes, get up and return to another space in the house to do a relaxing activity, such as reading or listening to music. Lying in bed awake can create an unhealthy link between your sleeping environment and wakefulness. Instead, you want your bed to conjure sleepy thoughts and feelings only.

如果你卧床20分钟后还睡不着，那就起来找个别的地方做点放松的活动，比如阅读或听音乐。醒着躺在床上会在你的睡眠环境和清醒状态之间建立一个不健康的联系。你不想躺着睡不着，你只想让你的床把你变困。

Wake up at the same time every day. Even if you have a hard time falling asleep and feel tired in the morning, try to get up at the same time (weekends included). This can help adjust your body's clock and aid in falling asleep at night.

每天在同一时间起床。即使你晚上很难入睡，早上又困得不行，也要尽量在同一时间起床（包括周末）。这有助于调整你的生物钟，帮助你在夜间入睡。

上述的建议你或许都知道，但是从来都是三天打鱼三个月晒网。这时候可以来点外力帮助。

老人家一般都睡得早起得早，如果你有条件，可以搬去和爷爷奶奶住一段时间。你不会忍心在他们睡了之后还四处走动弄出噪音，所以久而久之，你也就可以拥有“养生生物钟”了。

Notes

sensory /ˈsensəri/ adj感觉的；感官的

lapse /læps/ n小错；过失；疏忽；衰弱；衰退

entropy /ˈentrəpi/ n（物理）熵（系统或过程中不能用来做功的能量的度量）

automotive /ˌɔːtəˈmoʊtɪv/ adj汽车的；机动车的