Hitching a ride in a robotic car may cause motion sickness, according to a study from the University of Michigan Transportation Research Institute.
That's because the very thing self-driving cars free people to do – text, read, watch videos and work – are the activities that make some individuals prone to motion sickness. Moreover, people tend to gaze down when they do these activities, which increases the risk of motion sickness.
Anyone who has been driven on a curvy mountain road knows the driver has the best seat in the car. The driver has the optimal field of vision, a feel for the road and can anticipate the movement of the vehicle. That puts the driver's vestibular system – the parts of the inner ear and brain that control balance and eye movements - in sync. The brain likes that type of control and is less likely to protest with waves of nausea.
"By switching from driver to passenger, by definition, one gives up control over the direction of motion, and there are no remedies for this," researchers Michael Sivak and Brandon Schoettle wrote in their study.
Adults are more susceptible to motion sickness than are children, according to the study. The most severe symptoms can include vertigo and vomiting.
The study examined the frequency of motion sickness among auto occupants and the activities they said they would engage in if they were freed from driving.
The results indicate that 6% to 10% of American adults riding in fully self-driving vehicles "would be expected to often, usually, or always experience some level of motion sickness," the authors said.
Certain design changes could reduce the propensity of motion sickness in autonomous vehicles, Sivak and Schoettle said.
Designers could extend the field of view for passengers with large, transparent windows. They can also optimize the direction of the gaze by orienting video displays and work stands so that people look nearly straight ahead, or by having heads-up displays on the windows. They can also manage the physical position of passengers to reduce motion sickness. They could include fully reclining seats that would allow passengers to lie down flat facing up. Designers should avoid swivel seats.
The report noted that its calculations were based on the assumptions that the cabin of self-driving vehicles would be similar to that of today's conventional vehicles. If smaller, opaque, or reduced-visibility windows were employed in self-driving vehicles, the frequency and severity of motion sickness would increase.
"Conversely, if self-driving vehicles would provide a smoother ride than conventional vehicles, the frequency and severity of motion sickness would decrease," the authors said.
Google, Tesla, Mercedes-Benz, Nissan, Audi and many other automakers are testing self-driving vehicles. They could be sold within five years, depending on the development of federal and state traffic safety regulations.