Railroadin' (1929)

The gang is playing around the railroad station, and Joe and Chubby's father, an engineer, lectures against the kids playing in such a dangerous area. True to his word, after Joe and Chubby's father leaves, a crazy man starts a train with most of the kids on it, save for Farina who is nearly run over several times.
Once Farina manages to climb aboard himself, the kids attempt to stop the runaway locomotive, but have no luck until the engine crashes into a grocery truck. As it turns out, however, the entire incident is revealed to be a dream Farina had as Joe and Chubby's father lectured the kids about rail-yard safety.