I had an idea for adding some life to a background.  A lot of people like urban switching, and don’t touch passenger operations.  But subways or commuter rail, or even streetcars, are a frequent part of the suburban and urban scene.

One thing occurred to me, to make things livelier.   If you have a completely independent section of track that passes through the scene along the back, partially hidden, then an automated BUDD RDC, subway, or commuter rail train could pass along the back of the scene now and then.  Use an auto-reverser on each end, with a decent delay, every now and then, a passenger train passes through the scene.  If you want double track, use a spring switch at each end to shift the train onto the correct track.  The termini, of course, are completely out of sight behind buildings, in a tunnel, etc.