Self-driving cars are coming, that much is clear. Instead of worrying about how they'll interact with non-self-driving cars, or stop signs, it seems we should all be more concerned if they'll come with barf bags.

A new study conducted by Michael Sivak and Brandon Schoettle of the University of Michigan Transportation Research Institute (UMTRI) predicts that more people may get car sick once driverless vehicles reach the road.

For their study, UMTRI surveyed 3,200 adults from places around the world like the United States, China, Japan and the U.K. People were asked what activities they would like to do in a car instead of driving, like reading, playing games or talking on the phone.

More than a third of Americans would do things that increase the chance of motion sickness, according to the study. Half of Indians, 40 percent of Chinese and 26-30 percent of adults in Japan, Great Britain and Australia would engage in similar activities as well.

Some could even suffer extreme bouts if they're already prone to motion sickness in modern cars.

"Motion sickness is expected to be more of an issue in self-driving vehicles than in conventional vehicles," said UMTRI researchers Michael Sivak in a UMTRI press release. "By switching from driver to passenger, by definition, one gives up control over the direction of motion, and there are no remedies for this."

So how can people avoid throwing up in a self-driving car? Simply close your eyes during a car ride or even take a nap. Researchers also recommend watching the road or talking to a friend on your smartphone to distract your mind.

"The frequency and severity of motion sickness is influenced by the activity that one would be involved in instead of driving," Sivak said.

Sivak and Schoettle believe that companies working on self-driving cars, like Google, Nissan, Tesla and (possibly) Apple, would be wise to create self-driving cars with seats that can be fully reclined to restrict head motion and use large, transparent windows to maximize the visual field. 

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