My grandfather was an agent for the Santa Fe RR. If I was in his car on a road paralleling the tracks and there was a train, he knew the 'code' to honk in his Buick Roadmaster and the engineer would blow his whistle back at us. You can imagine the grin on my 10 YO face.
As a kid I saw the end of the steam era change over to diesel. They took on a modern look towards the end:
