During road trips, it’s not uncommon for drivers to look over and see passengers that have nodded off, their heads bouncing gently against the door window. Drivers sometimes find themselves fighting off drowsiness. And it’s not just long-haul truckers: Even an afternoon day trip can promote nodding off.

在乘车途中，司机经常会看到乘客们打瞌睡。睡着后的乘客的头在车窗上轻轻地撞来撞去。司机有时候也会犯困。犯困的不仅仅是长途卡车司机：即使是下午坐车外出，也会让人犯困。

So why do car rides tend to turn us into bleary-eyed husks in need of caffeine or blaring music to remain alert?

那么，为什么坐车会让我们睡眼惺忪并需要咖啡因或者大声的音乐才能保持清醒？

According to Sleep.org, drowsy driving is often correlated with “highway hypnosis,” a term used for drivers and passengers who see their need to pay attention reduced when they’re on a predictable and monotonous route. For road trips, this can mean staying on a highway for extended periods without needing to check for exits or navigate the sometimes-tricky paths present on side roads.

根据Sleep.org网站介绍，疲劳驾驶经常和“高速路综合症”有关。“高速路综合症”是指当司机和乘客处在一条可以预测且单调的路线中时，他们需要保持注意力的需要就会有所减少。在公路驾驶中，这意味着长时间在高速路上行驶且不需要留意出口或对岔路口有时看上去复杂的路况进行导航。

drowsy driving：疲劳驾驶

highway hypnosis：高速路综合症

The predictability promotes somnolence, or even a trance-like state. You might sometimes find yourself having covered a stretch of road without remembering much of it. And the longer the unchallenging drive, the sleepier or more unfocused drivers may become.

可预测性可以加重困倦和恍惚或甚至让人进入一种催眠的状态。你有时也许会发现自己已经开过一段路了，但脑海中却没什么印象。这种状态持续的时间越长，驾驶员就会变得越来越困或注意力越来越涣散。

Somnolence：困倦、恍惚

Trance：催眠

Road trips can also fall into a person’s natural circadian rhythms for increased drowsiness—typically in the early morning hours and mid-afternoons. A road trip that started out at 8 a.m., for example, and extends into 2 p.m. could see a vehicle’s occupants tired from both a routine highway circuit and the expected sleepiness they experience later in the day.

乘车外出也会成为一个人的自然生理节奏而使困倦加重-一般是在早晨和午后。比如，从早上8点出发，到下午2点的乘车外出时，车辆上的乘客因固定的高速公路路线和知道自己随后会犯困而感到疲惫。

circadian ：生理节奏

There’s also some limited research into the mechanics of a car affecting a person’s alertness level—specifically, how the vibrations of a moving car can relax the brain and body.

目前针对车辆对乘客警觉程度影响机制的研究还十分有限-特别是，行驶中的车辆的振动会使大脑和身体得到放松。

While a possible explanation, all we know for certain is that the lack of mental stimulus on a drive can promote fatigue. That can prove deadly, as the Centers for Disease Control (CDC) estimates up to 6000 fatal crashes a year are caused by drowsy or inattentive drivers. The U.S. National Highway Traffic Safety Administration estimates over 100,000 crashes a year involve people struggling to stay awake.

尽管这可能是一种原因，但是我们都知道驾驶过程中缺乏大脑的刺激会加速疲劳。而这被证明是致命的。疾病控制中心预计，每年最多会有6000例致命撞击事故由于驾驶员疲劳或不专注所导致。美国国家高速公路交通安全管理局预计，每年10万例的车辆事故中都和驾驶员疲劳驾驶有关。

To stay safe, it’s best to take breaks, switch drivers, and make responsible use of caffeine to promote alertness. “Tricks” like turning up the radio or rolling down the window haven’t ever been demonstrated to have a real effect.

要想确保安全，最好是采取休息、更换驾驶员并有效使用咖啡因来保持警觉。像打开收音机或把车窗摇下来这样的“小技巧”并没有被证明具有实际的效果。

If you’re merely a sleepy passenger, your risks are few aside from a slightly sore neck. Enjoy the rest.

如果你仅仅是一位睡意十足的乘客，那么你所需要付出的代价仅仅是脖子有点酸痛。你大可放心休息。

来源：Mental Floss   编辑&翻译：Sarah