"Unstoppable" has many similarities to a another movie released back in the 1980's titled "Runaway Train" Starring Jon Voigt and Eric Roberts. The basic premise of an unmanned locomotive running at high speed is present in both films. The possibility of extreme and/or toxic disaster is a plot device in both films. Also similar is the disagreement among railroad officials concerning how to handle the situation, with one official wanting to derail the train and another official not wanting to derail it. The moving of one train onto a siding while the runaway passes and crashes into the last few cars of the train pulling onto the siding is also present in both movies. In "Runaway Train" there is much concern that the speeding train will not make it across an old trestle. In "Unstoppable" there is much concern that the speeding train will not be able to negotiate a sharp curve. There are other similarities as well, but these are the major ones I noticed.