Let's hope they start bringing these cars to upstate New York in the winter, only then can we seriously consider Level5. The salt layers on so thickly that I would be surprised if LIDAR and cameras could work through that. I am not sure of any solutions besides adding little wipers for all the sensors to keep them clean or adding more repellent paint.
Google does have wipers on at least one LIDAR design. Another sensor cleaner alternates sprays of washer fluid and compressed air. We had that on our DARPA Grand Challenge vehicle in 2005. Ford has a camera cleaner on some 2017 Ford pickups.[1]
Pittsburgh, where Uber's ATC is based, is another profoundly challenging environment— there are a lot of curvy cobblestone streets with >10% grade that haven't been maintained in decades.
And the weather is often snowy or sleety or otherwise unfriendly.
Just remember that the extra sensors are a "bonus": if a human being can successfully drive by just using their two eyes in the driving seat, with perhaps 200° range and a couple of mirrors, then an AI can be trained to do the same.
