You must not live somewhere that gets a lot of snow :) For those of us that do, sometimes driving conditions are much less than ideal, even unsafe. Several times per winter I have to drive home from work on unplowed roads. As you put it, I have prior knowledge of the road (maybe precise GPS will help here?), and I can figure out where it is safe to drive based on tire tracks. I guess these will just be places that you probably won't have one of these vehicles (just as you wouldn't ride your motorcycle in such weather).