I don't see why not being able to see lane lines would be a the problem, at least for the full-fat Waymo solution. My understanding is they are using lidar sens

I don't see why not being able to see lane lines would be a the problem, at least for the full-fat Waymo solution. My understanding is they are using lidar sensors to correlate their exact position in addition to GPS which can be accurate to sub-meter level. In fact, they would have much more information to go on than most wet-wear drivers, assuming they can correlate the position of street furniture etc. The bigger problem I would imagine is finding the car not responding to inputs in a predictable way. I would image at a certain point they are going to give up. Even a human driver might need a push in some conditions.