During my first driverless robotaxi rides in San Francisco a year ago, the robotaxis had to stop carrying passengers at the first sign of raindrops or drizzle. A few months later, I was already able to drive them in heavier rain.
What exactly are the challenges for autonomous cars in the rain? Brian Wilt, machine learning expert at Waymo, broke that down in a LinkedIn post. He also posted a video of one such drive during the monsoon season in Phoenix, in Arizona.
Hardware problem (the car needs to clean all its sensors);
Perception problem (lots of shiny reflections, particles);
Control problem (different braking distances, avoiding hydroplaning);
Planning problem (deciding if it is safe to drive over this puddle/branch, traffic light failures, fallen trees).
In Wilt’s experience, there are also more pedestrians trying to get out of the rain and not paying as close attention to traffic. So, once again, a Waymo has to pay special attention to pedestrians during the rain.
This article was also published in German.