I have witnessed a large bus burn. This summer, on a trip to Chicago, we stopped at a rest stop in Wisconsin, where a bus had pulled over because the kids inside saw smoke rising from the rear wheels. When we pulled up, all the kids had safely evacuated the bus. The bus driver could not put out the fire that had erupted at the back of the bus. His small, red extinguisher was useless in comparison to the flames coming out of the bus. In the middle of nowhere in Wisconsin, firetrucks were not forthcoming. We watched the bus burn, then, for over 30 minutes. The flames slowly made their way to the front of the coach. It never exploded. When the fire reached the fuel tanks the fuel burned like a controlled blow torch. Some people around us said that this is the nature of diesel fuel, it just doesn't explode like gasoline would (I don't know if this is true). When the firemen arrived, the fire was put out in no time, and the bus looked like a burned skeleton as in the picture above.
Anyway, I learned three things from that event. First, large buses should be equipped with many large fire extinguishers. Small extinguishers aren't adequate to put out anything larger than a stove fire. Secondly, the allegedly 20 people who died on the road in Texas in a burning bus know what being burned alive feels like. Their pain is unimagineable. It is really unfortunate that they couldn't evacuate the bus before it was engulfed in flames. Was there only one exit? Finally, buses are liable to catch fire in hot, sunny weather. This is unacceptable. There is no reason that buses cannot be made safer.