No CGI here Moojgoo, the scene with the locomotive flying off the trestle bridge was accomplished by means of a 1/4 scale model of the engine and bridge, several cameras were placed around the smaller ravine that was used to capture all possible angles when the engine ran off the bridge. It was steamed up and ran under its own power off the bridge, hitting the ravine floor and exploding, doing this with CGI at the time would have been nearly impossible due to the enormous cost involved. The archaic computers of the time, and even had it been done the effect would not have been so good. The next scene shows the Delorean coming back to 1985 on the steel bridge that is there in 1985, I have for many years thought that particular two second shot was done with a very detailed HO model of the bridge and ravine. I hope this answers your question.
WileeCoyote
