They are faking their way through using a Lidar-heavy approach. When it works it's great, but when it fails it's dog level pathetic.
Waymo's safety data, on carefully curated paths, with human assistance and in the most car-centric cities in the world, is worthless. When these things hit the real world, with black ice, open manhole covers potholes etc. etc. don't expect lidar to save you from disaster. Maybe the average safety case can be made, but that won't be acceptable if they regularly kill people by confusing cows with flying plastic bags.