I was asked for a description of the drive board shown for the tunnel signal, which I also use for ground signals. So I might as well put it on here. ( Sorry, bit of a rough sketch) It really is simple, it doesn't have any fancy speed or bounce settings. Nothing into the relay it sits at one position, 12V in, it sits at the other. The bi colour LED would change from red to green if needed. The two 5k pots adjust the positions. If you need to the relay 0v could be separate from the signal 0v , then it would be isolated input. It also works fine with just a single 5k pot as a general servo driver.

Feel free to mess about.....