If you can manage, keep some fencing material in the vehicle, coiled or flat. Sometimes all you've done is simply slid off the road and you're just a foot or two off the pavement. Lay the wire down in the direction you need to go (right up against the drive wheels) and go as slow as you can. The fencing digs into the snow, the tires grip the fencing.

I keep some 2x4 welded wire fencing rolled up with duct tape, but a friend swears by chain link.

Sue