I have seen this video before. Pretty ominous watching the action behind the engines.
MY Uncle was a train engineer and he told me the reason that the flammable gas tanker are never placed at the end of the train is the fact that if another train runs into the back end of the train it dose not start a fireball. Apparently sometime in the past this has happened. The other reason a tanker is placed in the center of the train is the fact that if there is a head on collision with another train that there is some room before the tanker is hit.I found another reference to that video that mentioned there was a flammable gas called Ethylene Oxide
in the tank car.
I think if I was an engineer and could pick and choose, I would put all the nasty stuff at the back and have nothing but coal and empties riding up close behind.
Somehow though I doubt the extra time in the switching yards would be allotted to me.