Drive it in manual mode like we do right now? I mean even an autonomous car that could handle 80% of normal driving just fine would be great. And by 80% I'm talking about driving on a freeway without crashing into a barrier in broad daylight.

Gonna suck for those people who don't own cars and are relying on the fleets of privately-owned pseudo-taxis.

There have been a bunch of prototype self driving cars driving in snow. I'm not sure it's fundamentally a much different problem to self driving in general. eg https://www.engadget.com/2018/05/08/waymo-snow-navigation/

Sure they may perform worse in snow but humans do too.

I don't know if you live in such a city, but I can tell you that in mine the rare days it snows circulation is extremely chaotic, with people having slow paced crashes all over the place, and I'd wager AI is good enough to do that as well.

My understanding is that AI has different failure modes. If it doesn't see the road, it might not realise it doesn't see the road and just go off road. It's not necessarily going to react like a reasonable human.

I see your point, and it's indeed valid : I do remember a tesla crash where the autopilot simply followed an old line on the road instead of the regular one, thinking all was fine until it hit a column, killing the passenger.

But in this specific case of snow, I think this could be handled in a decent way by AI, as I would not expect snow conditions to be too hard to detect. Even something like "grip is not good enough for autopilot/snow detected on/around the road, stop on the side or slow down to the point of being impossible to have a fatal car crash until driver takes over" would be good enough.