I can give you basics on this topic only. The train whistle sounds when it reaches certain points on the track so the folks at the depot knows where she's at. The toots all mean something. You'll notice when the train stops for the robbery you hear several short toots in a row, which esentially means "Whoa, something weird is going on here! (Meaning the robbery)" When the train goes through Sweet Mary's Tunnel, it's the same blast each time, too. Steamfreak would be the ultimate insider here to tell you what the whistle is saying. Let's hope he chimes in here.