For the vehicle I carry a small light snow shovel and a pair of traction aids. And a car blanket. A bottle of water too, only because I carry one of those most days anyway. When I used to nordic ski I had a fanny pack on me of related gear (waxes etc) that included spare ski tips (for repairs) and snack bars. It was and is a big fanny pack. I still have it. The ski tips could easily be used to shovel if need be. Never had any emergencies. Snow shoes make great (powder) snow shovels. I have used them for digging a quick and snug spot out of the wind for lunch breaks. I and we often had ski poles also. Aside from their obvious use they also made great lunch break back rests, supports for extra layers strung out for wind breaks etc.
These days we are not so adventurous and rarely break our own trails, but a day pack with food, drink, and an additional layer each always makes the trip.