I worked at Big Thunder Mountain years ago and at that time it was the only roller coaster that could run five trains at one time. Bringing out the fifth train was very complicated. The instructions were about one page long and if you made a mistake it would bring the whole attraction down. When you hear the animated recorded spiel go off and the voice says "hats and glasses" the train should be leaving the station or you have problems. Its not that way anymore as Disney has done an update so that it is easier to operate the attraction.