I'm an avid railroad fan, and for all of its inadequacies, I feel that this movie still rates as excellent. I first saw this as a child, and have been searching for it for over fifteen years. I was lucky enough to find someone on Ebay that has a 35mm copy of it and does sell videos of it, so for all the true fans of this movie, check out Ebay.
As for the technical end of it, the plot is probably something that could not happen, at least in the magnitude depicted here. ALL diesel locomotives have something called a TRACTION BRAKE, which, like the reversal of an airliners engines to slow an aircraft, does essentially the same thing. The traction brake reverses electrical polarity to the motors, causing them to act AGAINST forward motion. This is comparable to downshifting an automobile transmission into first or low gear when descending steep hills. By itself, the traction brake could not have stopped the train, but the locomotive could have slowed the train down to a less than fatal speed. Also, a helper locomotive added to the rear of a train would probably not have the power to stop a train travelling 70+ mph by itself. It would need the assistance of the air brake throughout the train to accomplish that - which was useless in the movie plot, and even if it weren't, there's no way the air hoses could be connected on a moving train.
Despite these flaws, the movie is very entertaining, and at 70 minutes, it is like a sweet and satisfying snack, compared to a 120 minute main course.
