If the results of a new study by researchers in Australia hold true, cars of the future might not vibrate their drivers.
There’s something about highway driving that’s a better sleep-aid for me than Benadryl. I’ve tried to research why this happens and what I can do about it—à la Google—but the solutions are no more revolutionary than: roll the windows down, blast music, drink MORE coffee. Science is sort of starting to catch up to this problem; maybe this latest study will motivate more research.
Some scientists believe that the vibrations from a moving car may contribute to the sleep-inducing, hypnotic effects of highway driving. But no one seems clear on why or how this happens. Even whether or not whole body vibration contributes to drowsiness is up for debate.
A study conducted on rats from the early ’80s may offer some clues, though. Researchers from Kanawaza University in Japan subjected rats to various frequencies of whole-body vibration (5, 20 and 30 Hz) and then measured, among other things, the amount of serotonin in their brains. The researchers saw that within the brain, serotonin levels increased after the rats were gyrated in an electromagnetic shaker for 240 minutes.
Serotonin is a neurotransmitter, a molecule in the brain transmitted between neurons, that plays several roles in the sleep-wake cycle. Since an increase in serotonin in certain areas of the brain occurs when the body falls asleep, maybe, possibly, somehow when humans experience similar vibrations, this is the mechanism that leads to drowsiness? But apparently, no one knows.
More recently, a group from Australia released a manuscript (that has not been revised and officially published yet) showing how the vibrations drivers feel from the car can lead to sleepiness.
These researchers conducted a small study in which subjects “drove a car” on a “highway”. The subjects did sit on a typical car seat, foot on the accelerator, hands at 10 and 2 (presumably), but the rest of the car was missing for this simulation. The “highway” was merely a monitor displaying probably the most boring scene ever: a two-way straight highway. The seat was affixed to a vibration table that simulated the low-frequency vibrations, between 4-7 Hz, one might experience in a car.
According to one hypothesis, drowsiness manifests in a loss of neural processing efficiency, resulting in greater amounts of brain tissue recruited to perform a task that would not require such processing power during an awake, alert state. The researchers used this definition for drowsiness in their experiment. The experimenters believed that people driving while drowsy would recruit more brain areas in order to pay attention to the road and become stressed, activating the sympathetic nervous system and causing a variable heart rate.
Participants, fifteen undergrads in all, had to keep “driving” for an hour, maintaining a speed of 160 kilometers per hour (about 99 miles per hour). Participants also had to come in to complete the study an hour before their usual bedtime. The researchers chose such a high speed and such an inconvenient time for a road trip because the conditions demanded greater concentration from participants already on the cusp of drowsiness. Since it increased the workload required of the participants, it also induced drowsiness in a timeframe convenient for the experiment, 60 minutes max.
While participants spent an hour driving nowhere, a wireless sensor measured heart rate and transmitted information via Bluetooth to a smartphone.
As part of the experiment, the same group ran through a second simulation as well (either the day before or the day after the previously mentioned simulation, researchers randomly determined the sequence), doing all the same things as the experimental condition—but without the vibration.
After analyzing the results, the researchers found something I will use my editorial power to describe as: potentially concerning. When the participants experienced vibrations, they reported significantly higher sleepiness scores (according to a validated, but subjective measure, the Karolinska Sleepiness Scale). They also had increased activation of the sympathetic nervous system, which the researchers believe represents increased stress stemming from trying not to fall asleep while driving.
Another driving simulation study published last year came to similar conclusions–that low-frequency whole body vibration is associated with drivers’ reported drowsiness as well as swerving from the center of the lane during the simulation.
While these findings still need to be replicated in a larger, more representative group, the possibility that car vibrations may lead to drowsy drivers will hopefully lead to more research in this area. Whether or not anything comes of this most recent study in particular, ideally, sometime soon, those of us susceptible to highway hypnosis will be able to drive without a cup of coffee in every cup holder.