Waymo claims: "“Waymo provides more than 250,000 paid trips every week in some of the most challenging driving environments in the U.S..."

But also: "The company operates more than 1,500 vehicles across Los Angeles, San Francisco, Phoenix and Austin."

So not in the snow, ice, winding mountain roads, or any really "challenging driving environment"... more like flat city streets, hilly city streets, a desert, and giant, flat, sunny roads.