The predictability of the train can be good. While I can't find it at the moment, there was an article I recently read about how repetition (in the context of

The predictability of the train can be good. While I can't find it at the moment, there was an article I recently read about how repetition (in the context of Good Night Moon(?)) and the ability to be able to predict the future is useful for early childhood learning and development. A train is very predictable - the sound, the motion, the path... for the same reason that children like having the same book read to them again and again, the train fills that role too.