[dsr_]

Having lived through many such blizzards, there are two things that humans do:

The smart ones pull over and turn on the emergency flasher. Then they check to make sure they have lots of gas, blankets and water, just as they prepared.

The dumb ones slow down to 45 mph and stare into the white blankness looking for clues about curves.

[stuckagain]

Exactly! Every question about how a computer-driven car will handle exceptional situations encountered by humans shares the same answer: the computer won't have got itself into the situation in the first place. Humans might drive a car into a whiteout blizzard, but that only serves to demonstrate the urgency of cutting humans out of the loop.