James Peng, cofounder and CEO of Chinese robotaxi startup Pony AI, was reviewing customer data with his team, and he was facing a puzzle. Every day, one of his users would book a robotaxi at the same time: right after lunch.

“After a while, we called him and asked why he always took a ride at that time,” Peng recalled to Fortune.

The user’s answer? “The environment is great. It’s clean. I use it as my napping place!”

For Peng, the regular napper is a sign of how quickly riders are adapting their behavior as self-driving cars start to take over China’s—and the world’s—streets.

Chinese robotaxis are plying the streets of cities like Guangzhou, Beijing, and Shanghai. And much like how Waymos are transforming user behavior in San Francisco, robotaxis like Pony AI’s are changing what Chinese passengers are doing.