When a problem with our crossing gates is reported, the trainmaster issues go-slow orders and all trains go back to sounding the horn until the problem is corrected.
I just feel better with the horn - one more chance for me to be warned of the train, if the crossing signals aren't working and somehow the engineer doesn't get the word. But most of the neighborhood is just annoyed by the noise.
We almost had time to get that Jeep off the crossing when we heard the horn, if I hadn't had to throw the dogs in the house before I got in the truck we would have done it.
If the transmitter works, people near the tracks are spared the noise of the horn. If the transmitter fails, the engineer sounds the horn as he would if the system did not exist. If the system is designed to fail "safe" (which would not seem overly difficult) what's the problem?