59 minutes ago
Monday, May 10, 2010
Posted by Mojo at 5:00 AM
I finally had to look this up because the curiosity was killing me.
Turns out that "humping" is a method of sorting and coupling (oh grow up!) freight cars to make up trains. The cars are pushed to the top of a man-made hill (a hump) and over the other side where a series of switches routes them to the proper train. This method is much faster than shuttling cars hither and yon with an engine, but isn't so friendly to certain types of cargo since the impact of the two cars slamming together can damage one or both. Cars with these kinds of loads are marked "Do Not Hump" so the crews will know to set them aside for special handling. (Source: The Straight Dope: What does "DO NOT HUMP" mean on the side of railroad cars? 7.4.1986)