I'm not sure what "90% safer" means. Say human drivers have one accident per X miles, and Waymo is "90% safer".
Would that mean Waymo has an accident 0.1 times per X miles? Or .45 x accidents per X miles? I'm confused. So, I looked it up. This makes more sense, to me.
Waymo estimates that typical human drivers would have gotten into airbag-triggering crashes 159 times over 96 million miles in the cities where Waymo operates. Waymo, in contrast, got into only 34 airbag crashes—a 79 percent reduction