Or as we "say" it hatsjoe
Though I can see toot toot instead of choo choo, choo choo is definitely not the sounds of the wheels being turned.
To stop all the arguments and make the question less ambiguous I would also suggest using train instead of train whistle.
(even looking at it now train whistle choo-choo looks weird to me, a whistle doesnt say choo choo, but pffrrrttttt!! in my personal experience ;) train signal allready seems better)