As described above, the proposed device already has two relays on board. My thought is to have one relay remain on while the crossing is active, and the other toggle on and off. The steady relay will apply power to the common of the other to provide for flashing lights, but can also be connected to crossing gates.
In NO case will Arduino pins be connected to anything in the outside world. For most users, the relays will provide on/off functionality for whatever device is connected. For the rare user that wants a logic-level output for connection to some other device, the logic level output will be isolated from the uP with an optocoupler. The uP will only ever be driving LEDs and optocouplers (more LEDs)
Anyway, consolidating the list, Standard and Delay turn-off are the same thing. Both modes of Enter-on/Exit-off look like they are the same as well. Finally, mode 1 and 3 of the directional function are the same.
JGL
