I would assume that if you get in an accident in fog stay in your vehicle until at least another ten or twenty vehicles have joined the pileup. You are safest in your own vehicle with your seat belt on than being outside. One the ten or twenty vehicles have joined the pileup then there should be enough vehicles in place to slow down any incoming trucks.

Of course if a fire starts nearby then get the heck out. And walk up the highway. Not towards incoming traffic. Keep the pileup between you and the incoming vehicles.