Thankfully it doesn't sound like there were too many injuries. We had a massive pileup here many years back due to fog that killed 8 people and shut down the road highway for several months so it could be repaired.
I remember driving to work that morning (not on the highway, but nearby) and keeping an eye on the cloud cover that hung about 10 ft off the ground. Since then, I don't drive in conditions like that. If it looks like thick fog can drop, I get off the road and wait it out.