I have seen those signs before. I didn't know what they mean.
Info for Emergency Services and Breakdown/recovery so they can identify the contents of the tank and know what safety precautions to be taken if the vehicle is immobilised for any reason.
Obviously not readable in this conflagration!
I didn't know about the explosive tires. In the movies you always see people trying to run away from a burning vehicle before it goes up in a gigantic ball of fire.
I recall reading a post here concerning a SimHQ member pulling victims from a vehicle that had rolled down a bank. Other bystanders were reluctant to get involved as they imagined there was danget of explosion thanks to film and TV.