There are four railway stations, with a classic rail switch system.
But the peculiarity of this system : -there is ONE rail switch (instead of 4)
                                                             -EACH STATION (4) can send a wagon to one of the 4 stations.
In each station, you press a button, the wagon automatically goes to the chosen station, automatically resets the rail switch system, and can be reused by the aforementioned station.

The advantage of this system : 4 players can remotely use a rail switch system, and at the same time. This can serve as a mail service, for example.

Of course, you can build stations away from each others as much as you want (I built nearby stations).
Right now, I am considering a more compact system.