June 3, 2019—In a world where everyone’s a passenger, car sickness could run rampant.

Volkswagen is putting research into reducing the motion-related malady with an eye toward an autonomous vehicle environment. After all, it’s passengers who are most susceptible to car sickness.

“To put it simply, the forces acting on us in the car confuse our sense of perception,” said Adrian Brietzke of Volkswagen Group Research in a press release.

VW said this happens most often to passengers who don’t have the “driver’s privilege” of knowing what’s about to happen next allows them to adapt to the car’s motion.

In a test, a volunteer hopped into the passenger seat of an Audi A4 on a closed track. VW outfitted the volunteer with sensors to measure her pulse, skin temperature and changes in skin tone.

The volunteer watched a tablet fixed to the dashboard that played swimming fish videos. She also logged her “state of health” on the tablet as the Audi took a 20-minute drive behind a semi-autonomous VW Passat.

“I didn’t think I was that sensitive, but I felt queasy after just a few minutes,” the volunteer said, according to VW.

The company has looked into ways to communicate an autonomous car’s actions to the passengers in an attempt to reduce sickness. One idea was to put LED lights into the door panel that change color to give the passenger a cue for braking or acceleration.