I went as saw "Unstoppable" yesterday. It's actually a decent movie, mainly because of Denzel Washington and Rosario Dawson. And for those simpletons going "just make it go in a circle, lol" or "turn it off, duh" - that's not how trains work. They do a good job of explaining why in the movie.
It's diesel engine that left the yard under full throttle, carrying 39 cars, 8 of which are carrying a toxic chemical used for industrial purposes. It cannot be shut down remotely, and there isn't a "big circle of tracks" you can put it on once it has left the yard. The tracks pass through several towns close together, and if it derails the chemicals will essentially make the town unlivable, in addition to killing anyone within a few miles of the scene.
Stuff like this isn't supposed to happen, and they show the failsafes that are supposed to prevent it, and how those failed, and how it got away. (Due to human workers not following proper safety guidelines, even as people are yelling at them to do so.)
It's intersting just as much for the glimpse into the train industry as it is for the disaster drama. Because you know they'll find a way to stop it before the movie is over, the only question is how.