Twins in car, with one asleep at the wheel. Researchers found that just 15 minutes of car-like vibration was all it took to make people drowsy. (Photo: propositive/Shutterstock)

You're straddled in nicely. Your heated seat just reached peak toasty. And there's a soothing melody on the radio.

It would seem like the perfect time for a nap. If only you weren't hurtling down the highway at 60 miles per hour.

It doesn't help that your car is also giving off sweet vibrations — literally.

In fact, according to a new study from Australia's RMIT University, the gentle vibrations of a car in motion may have the most dramatic impact on our alertness.

In a series of tests, researchers found even the most wide-eyed and well-slept drivers needed only 15 minutes behind the wheel before they took a turn for the drowsy.

It was even worse for people who were already tired.

"We know one in five Australians have fallen asleep at the wheel, and we know that drowsy driving is a significant issue for road safety," research team member Stephen Robinson explains in a press release.

"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,"

For the study, the team observed 15 people in two simulated driving scenarios. The first involved a whole body vibration delivered through the car seat, set at a low frequency to approximate that of a car or truck in motion.

The other simulated ride was vibration-free.

Each driving test lasted 60 minutes. During that time, people who felt the vibrations embarked on a very dark journey.

"From 15 minutes of getting in the car, drowsiness has already begun to take hold," Robinson noted. "In half an hour, it's making a significant impact on your ability to stay concentrated and alert."

In 2013 alone, the the National Highway Traffic Safety Administration tallied the drowsy driving toll at 72,000 crashes, 44,000 injuries and 800 deaths. Considering the advances car makers make every year in coddling motorists with the latest comforting technologies, it's unlikely that number has only accelerated.

After all, we already put too much mileage on our bodies and stretch our days to the breaking point. In fact, according to a 2016 study from the Centers for Disease Control and Prevention, one in three Americans aren't getting enough sleep.

What happens when you put a weary, work-addled American behind the wheel of a car with a six-speaker stereo system, plush reclining seats and an (optional) DVD player?

Good night, sweet prince.

Man asleep behind the wheel. To sleep ... perchance to die? (Photo: milias1987/Shutterstock)

It's no wonder pedestrians, especially seniors, are looking both ways — and both ways again — before hustling across the street.

So the next life-saving car safety feature?

"To improve road safety, we hope that future car seat designs can build in features that disrupt this lulling effect and fight vibration-induced sleepiness," Robinson says.

But maybe we've just hit a wall of over-engineering Maybe it's time for a new way of thinking — something that takes a very different road.

How about a car that's engineered to actually keep you on your toes while driving?

Retro car drawing Forget leather seats. How about wicker? (Photo: AVA Bitter/Shutterstock)

It will take a bold automaker to introduce church pew seats, vents that randomly spew ice water in your face and maybe even brakes that require you to put your feet on the pavement.

And how about replacing cruise control with snooze control — essentially a big red button you push when feeling drowsy that electrifies the steering wheel?

Okay, so maybe we'll just have to wait until robots finally take the wheel from us — for everyone's safety.

That way we can sleep all the way to the office. And no one gets hurt.

Cars are engineered to put us to sleep
Researchers find car vibrations make even the most alert people drowsy.