I said I do this when it gets "dicey". "Impassible" is something different entirely. For that, I re-route.
I imagine though you must see some pretty severe snow. We got 13 inches last week and I simply can't find a route to work. The streets are plowed somewhat but I end up walking much more than times affords. (Luckily I'm on a good bus route...)
I see Montreal just got 45 cm of snow the other day. I imagine upstate New York must get snow like that once in a while...