For this challenge theme I would choose a detail. There is a lot of nice details in this train, which could give more interesting composition for straight lines. I wonder why did you choose this side of it, which is in a deep shadow? Nice subject, anyway. Good luck.
Good angle to show off the lines of the train, but perhaps just a hair dark on this side whch makes the lead car look a little black-blob-ish. A bit more light would bring out the detail of the side rails on that car - either a different time of day or perhaps a flash? Still a good take on the challenge.