Where does it go?
They DON'T just flush raw sewage out a hole in the bottom of the train onto the tracks do they?
And if they DON'T why does it say 'don't flush when the train is in a station'. What would happen if you did?
Or is it like aeroplanes where they freeze the effluent into turd and piss ice cubes and then press the button and let them out into the ether where they vaporise (this may not be strictly true).
Does anyone know what happens to shit on trains?