I read most of the posts, but got tired about 3/4 of the way down. Engine 143 or The Wreck On The C&O or The FFV was mentioned above as being by Joan Baez. In the Johnny Cash movie Walk The Line, Johnny, as a young boy, is listening to the radio late at night and we hear a bit of Engine 143 sung by The Carter Family.

Railroad Lady, also mentioned above was co-written by Jerry Jeff Walker and Jimmy Buffet.

Washboard Hank's Trainyards is a super song as is Roy Payne's The Trains Never Stop In Kingston Prison.
Has Fred Eaglesmith's The Rocket been mentioned?

I love Utah's Going Away (I think that's the title). It goes:

Is that the moon I see going down in the West,
Or just a headlight's glow; C&O Express?
I know she's gone, whatever I say
And it won't be long till I've made up my mind
And gone away.