oh, I had overlooked that.
Yeah, I used to be a warehouse manager for a large electronics and screen print supply manufacturer and would drive a delivery can with chemicals when a customer needed something much sooner. I had to spend a full week studying for the 49 CFR + additional hazmat training and then take their tests back in the 90's. From what I understand the use of software systems (which supposedly do a lot of the work for you) have lowered the requirements for people who do this for a living.
Yes, it's rare for a semi truck and trailer to crash like this, but we have these laws because when it happens, we need to know what's in the truck. Beyond that, the people loading these trucks should be trained and a dispatcher / warehouse operations manager should have never let these compounds go out together on the same truck ... this is a guess on my part, but it's probably an oxidizer or some type of agent that created great heat and flame when it reached flash point and then it set off the igniters in a sudden and swift chain reaction. Just like one big bomb.
I mean, look at the sides of that trailer. It looks like it's a flatbed trailer, but that's because it exploded!