Just a quick note - I happened upon a major 3-vehicle accident today on my way to a picnic. We rolled up moments after it happened.
My wife dropped me off, she continued to the picnic, I worked with the medics as we awaited extrication crews.

Vehicle 1: Minivan, 3x Passengers, 2 with major trauma, 1 serious.
Vehicle 2: Another Minivan, 3X passengers, all minor injuries
Vehicle 3: Pickup truck, 2x passengers, 1 major trauma, 1 serious injuries.

It was hectic, to say the least.

I worked vehicle 1, which was rolled onto it's side, into a large rock and on top of the other minivan. Both driver and passenger moderately entrapped. They missed some kind of a surface pipe by under 4", it looked like an inverted letter "J", and it was connected to a natural gas pipeline. I think that was good, I don't know what would have happened if they hit it, if it could have made a gas leak or not.
But the amount of crap in Minivan #1 was incredible, and it had all slammed up into the front (including a fire extinguisher that had been "attached" only to plastic, not metal, as I could see the plastic still attached to the mounting bracket.) Just getting all the crap out of the way to get to the patients took at least 2 full minutes, and we were working before the extrication crews got there. Not long for some patients, but an eternity when you're bleeding out. Pillows, tool boxes, coolers, blankets - lots and lots and lots of stuff. Secure your stuff, strap it down, do as much as you can to keep your stuff from being an impediment to rescue.

Just some perspective here from the front lines of the usual highway carnage.