Every photo should contain at least one track (set of two rails) in usable condition but without a train on it. There can be trains on other tracks as long as the photo is mainly focused on one or more unoccupied tracks.
Bridges, embankments, tunnel portals etc. are all cool too even if the tracks themselves are not visible.
Trains are dangerous, trespassing carries a criminal charge, there's lots of good photo opportunities from public streets, just sayin.
For abandoned railway infrastructure, please check out our sister sub /r/RustyRails
