Before he can be turned into human hamburger, Kimble manages to free himself, and he goes off to track down the man who murdered his wife. So the train scene is really what sets off the entire movie, and it was so important to the filmmakers that they actually demolished a real rail car and bus to film the sequence, which ultimately amounted to 60 seconds of footage. And then, after 10 weeks of preparation and $1.5 million, everyone packed up and ... left the remains of the horrendous crash by the side of the rails. It's still there:
As a warning to other trains and buses.
The crash was filmed outside of Dillsboro, North Carolina, probably because all other locations gave funny looks to the film crew when they said they wanted to destroy a train and just kinda leave it there, you know? While The Fugitive producers weren't total litterbugs and had one of the engines reused by the local railroad to pull a dining car, they didn't know what to do with the rest and figured a friendly junkyard owner would come by and take it all away. But that never happened, and to this day the crash is still on the side of the Great Smoky Mountains Railroad, where it has become something of a minor tourist attraction.