For me a moving train and its passengers were always dancing very lightly each in their own territory; the passengers in the cabins and the train on its rail. When I started animating it , I found out that a train is revealing its rough scary nature. You feel some moments passing slowly and peacefully in the train. You imagine the passengers being hypnotized by the repetitive sound of the wheels. You start to show and to depict this imagination but the train passes very fast.