The engine of the train had been switched front to back in the middle scene of the train trip.
The first car of the train would definitely not be used in a passenger train and must have carried the crew's equipment. Placing the safe car in the middle of the consist prevents passengers from going from the tail to the head of the train. The first explosion breaks the air brake circuit, then the whole train should stop, not only the tail cars.
In an early segment, a TV news update announces a big clue about the crook known as The Brain. He has a very large cerebrum and under stress or anxiety, his neck can't support his head. So, his head drops to one side (left or right). The next scene shows Col. Matthews with his head dropping to the side. He is then identified and flees in a police chase. He holds his head upright with his hand until he gets into his limo and escapes. But he never has another instance in which his head drops in the film. Not even in several scenes that would be highly stressful to any human being - i.e., when his apartment is all but destroyed, or when he's stuffed in a box, or when he's being chased and shot at.
Halfway through the film, when the train is shot from above in the countryside the shadow of the helicopter flying over is clearly visible on the side of the rail-track.