Won't work with just a loco right now, sensor 1 and sensor 2 are too far apart. Loco + 1 car will work though. I currently have a 'warn for 10 seconds' thing built in to allow the train to reach the exit sensor. Then after 10 seconds the warning continues until the exit sensor is clear. Gotta figure out how to handle this part better though.
When installed on the module, sensor 1 and sensor 2 will be just closer than the length of a short loco (GP-38 or F7 or something).
I see. I originally mentioned that the speed (and also direction) sensors should be close together. That way you can detect short trains. That pair of detectors should also provide you the direction of travel info (by looking at the sequence in which the sensors were covered). That way if a train (short or long) enters the crossing's detection block but then stops and backs out without ever getting to the crossing, your circuit will be able to detect that and take appropriate action (raise the gates). At least that is how I would envision it.