I know nothing about photography but I'll offer my input on each of them:
1) I like the shadows cast by the 66, the haze/dust.
2) I like the symmetry between the yellow of the safety line and then the class 31 and there seemed something symbolic that the light on the right hand side wasn't shining directly on the locomotive.
3) Contrast between Green and Yellow. I also liked the simplicity.
I voted for 2.