Why Riding as a Passenger Can Make Us Sleepy

Learn why riding in a vehicle of any kind — whether boat, car, plane, or other — can make us drowsy, plus how to take advantage of sleep time as a passenger.

Wide shot of girl sleeping on flybridge of yacht while on vacation.
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My dad has always loved fishing. So by my first birthday, I’d already logged plenty of hours on a boat. Some of my earliest memories as a toddler involve me curled up with my blanky and teddy bear in the bow — drifting in and out of a nap — while we trolled for walleye. The combination of the summer sun warming my body, the water lapping against the hull, and the humming motor would put me right to sleep.

Fast forward 20 years to when I landed a job as an editor for several boating and fishing magazines. The role required me to travel all over, spend time on people’s boats, interview them, and write about their adventures. A photographer took candid shots for the glossy spreads. The job was perfect. After all, I loved being on boats.

There was just one problem: Instead of capturing interviews, I really wanted to curl up and drift off. Most excursions began in the wee hours — for catching both the sunrise and the potential fish. But idling out of a long no-wake zone in the dawn glow was an almost-Pavlovian recipe for a quick snooze. No amount of coffee in a to-go cup solved the issue.

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Why does travel in vehicles make us sleepy?

Musician Shakey Graves has a similar lifelong love of sleeping while in transit. As he said in episode two of “Sleeping Around With Dr. Chris Winter,” while chatting with Winter, “My parents figured out that they could just put me in a car seat and drive me around the block, and I’d go to sleep. From that, I’ve always loved sleeping in cars.” Graves says that the ability to sleep isn’t limited to cars but involves other methods of transportation too, including planes. And he’s not alone. For many people, travel on a bus, plane, boat, train, or car is a recipe for a good snooze.

A couple sleeping on a bus.
Cute Siblings Sleeping On Bus
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Vibration makes us drowsy

“Low-frequency vibrations can stimulate the parasympathetic nervous system,” says Jade Wu, Ph.D., a psychologist, Sleep.com sleep advisor, and board-certified behavioral sleep medicine specialist. “This is the ‘rest-and-digest’ system (as opposed to the ‘fight-or-flight’ system) that can induce relaxation and drowsiness.”

A small 2017 study looked at the effect of low-frequency vibration on sleepiness and heart rate variability. Fifteen study participants engaged in two simulated hour-long driving tasks. One task involved low-frequency vibration, while the other did not. During the driving task with vibration, participants grew increasingly drowsy within 15 minutes.

As a driver, you can take steps to remain alert, such as opening the window or blasting the AC, listening to upbeat music, stopping frequently, staying hydrated, or drinking a caffeinated beverage. If you’re tired though, you should always err on the side of caution and stop and rest until you feel ready to drive again. But if you’re a passenger, you may not have the need to stay alert and will let yourself succumb to sleepiness from vibrations.

For example Winter says he falls asleep in an instant on a plane. “I fell asleep so quickly on a flight once,” he recalls, “that my perception of things was that we taxied out a little and turned around to go back to the gate. When I asked the man sitting next to me, ‘What’s wrong? Why are we going back?’ he responded, ‘We’re here man!’”

Similarly, Graves said, “Anything that vibrates a little bit ... it goes back to having my dad or someone that I trust driving a car and me knowing that I was sort of in a little ASMR-sleep, kind of contained space.”

White noise makes us sleepy

Another factor may be that the engines from our modes of transportation provide soothing white noise. If you do an online search for white noise, you’ll find everything from ship engine room to jet airplane sounds.

White noise has been shown to improve sleep quality in various small studies, especially to block out disruptions at night, but more research is needed. However, if you’re accustomed to falling asleep to white noise in your bedroom, then travel in a car, plane, bus, train, or boat may cue your brain that it’s time for slumber.

We’re likely wired to sleep in motion

Our propensity for falling asleep as a passenger may also have something to do with our biological beginnings.

“Fetuses experience whole-body low-frequency vibrations all the time in the uterus from the mother’s movements, heartbeat, and other bodily functions,” Wu explains, “which is why rocking and gently bouncing newborns can simulate the sensations of being in the womb and put them to sleep. Perhaps adults retain some of the association between rocking and drowsiness.”

We might be overly tired while traveling

“If a person usually doesn’t get enough sleep or is overstimulated,” Wu says, “their brain is always trying to find an opportunity to fall asleep.”

Whether you’re taking a vacation, visiting far-flung family or friends, or traveling for work, the act of travel itself can disrupt your normal routine, cause jetlag, or sap your energy. When you finally get the chance to sit for a length of time, your body and brain may take the opportunity to relax — even when you don’t want to.

“During residency training, when I almost never slept enough,” Wu adds, “driving more than 15 minutes was dangerous because I would reliably get drowsy after that long on the road. For long trips, I had to take precautionary naps before and during the trip.”

The journey might be boring

Sometimes your journey is monotonous or dull, and our minds simply care more about our pending arrival. Both Wu and Winter say boredom might take over. Or perhaps the passing landscape is a bit hypnotic, Winter adds, lulling us to sleep as a passenger. Whether your internet connectivity is limited, the scenery is monotonous, or you’re just deprived of the typical sensory overload of life, there can be a daze-inducing quality to time on a boat, bus, plane, car, or train ride.

How to sleep well as a passenger

If you’re en route somewhere, you might be hoping to take advantage of the low-frequency vibrations, white noise, and uninterrupted travel time as a passenger to get some Zzz’s.

But, Wu cautions, you may wish to skip out on sleeping during a daytime trip so that you get a good night’s rest once you reach your destination and so that your circadian rhythm isn’t affected.

If you’re on a red-eye flight or another type of overnight trip, however, getting some sleep is a good idea. Wu recommends using an eye mask and neck pillow and wearing comfortable clothes. Earplugs or noise-canceling headphones may also help.

“But don’t worry about it if you don’t end up sleeping much,” Wu adds. “Our sleep is very resilient, and it’s perfectly OK to experience an occasional disruption due to travel. You can simply catch up the next night.”

What to know about sleeping on a vehicle

We might be susceptible to sleep while in a car, bus, train, plane, or boat because of multiple factors, including the vibrations and the white noise, the sensations representative of being in the womb, the boredom, or simply the fact that we’re tired.

Of course, some people are immune to falling asleep while traveling. “This probably means they’re well rested and don’t need any sleep at the moment,” Wu says, “or they have insomnia and have difficulty falling or staying asleep in general.”

But for me, someone who battles insomnia, it’s always gone like this: Put me in a bed, and I’m alert as an owl; put me on a boat, and I’m ready for bed. Is it time to research houseboats?