Signals -- semaphore or colored lights or any other kind, solo by the side of the right of way or attached to overhead towers across the tracks -- have the deepest appeal for me.  They have found their way into many photos I've taken over the years, although only a very small number are posted to these pages so far. 

This view is from along the Cumbres and Toltec Railroad, straddling the Colorado - New Mexico border.  An old semaphore pokes up by the roofline and some nests.  The sky is an intense blue.