Stephanie, a tech worker from San Francisco, thought riding in a robotaxi from Waymo was the safest way to travel. Without a human driver, she felt more secure, especially as a woman. She didn’t have to worry about getting into a car with a stranger. Waymo’s self-driving cars take people around the city every month, and she was one of many who trusted them for their daily rides.

But one night, Stephanie’s ride took a frightening turn. She and her sister were in a Waymo Jaguar SUV, headin...