A technique I have long used for finding photographs is moving before stopping. An area, object or moment captures my imagination as I pass, and I then proceed to work at an image (Harry Callahan walked to do this; I tend to drive, due to the massive expanses of the West). In the case of this image, the billboard first captured my attention, and after working the image for more than an hour, I finally settled on this composition, and waited for a train to pass.