Trainspotter (UK), rail fan, train buff, railroad enthusiast, follower, foamer, as well as some names in local areas.
A note about foamers.
The term "foamer" came from northern California, where the "Feather River Route" of the now absorbed (by Union Pacific) Western Pacific Railroad ran along the Feather River between Portola, California, and Marysville, California.
Along this route, the "foamers" had to be in the water to capture their best photographic angles. Also along this route, the river is turbulent and pools form along the backwashes and eddys and usually sporting foam or froth floating on the surface. As the enthusiasts were at that point in the foam, hence the term "foamer" was applied and, apparently, stuck.