Corrected entry: As Al the Engineer falls off the train, two switch yard workers are standing beside a tank car. If you look at the logo on the car, it says "BA&P", which stands for Butte, Anaconda & Pacific. This is a railroad located in Montana, where some of the filming was done, but the movie is supposed to take place in Alaska, on the Alaska Railroad. The film crew obviously missed this.
Corrected entry: When Barstow gives the signal maintainer at Jordan orders to derail the runaway train, there is a shot of him crossing the track to get to the manual switch. In this shot the camera is standing on the track looking the way the train is going. Look behind the signal maintainer further down the track. There is a lot of freight cars parked on the same track.