In Gisborne, there is a lighting control unit that allows the tower controller to halt all trains before they reach about 50m from the edge of the runway. The default is to allow planes the right of way. When a train arrives on the scene(the tower controller gets an aural warning as well as a visual one on the panel) and the ATCO is happy with spacing, s/he allows the train to cross by way of a green signal to the train driver.
It's worked well for the better part of a half century although there was an anecdote told about a red-faced ATCO who forgot, in a quiet moment, to turn the signals back to the planes-have-right-of-way and only caught the impending disaster at the last minute. Result: train had squared off wheels after some emergency braking. Don't know if that's true; perhaps someone could verify?
I think Australia had one of these airports in the past, at least. Is that right?