I worked the night shift as University Police Officer. The University abutted railroad tracks. Every night (when on time), the Amtrak would come by just after midnight. I would be in the parking lot, I would put my light bar on & the conductor always gave the whistle on his train back to me.

When I was a kid on a road trip with family (40s) I'd see a big rig and raise my fist, pump it up and down, and get a satisfying blast from his horn.
Such fun.