We have developed a system called S⁴ - Station Shunting Scheduling System. Shunting schedules at railway stations are now scheduled manually by experts. It takes hours to make the shunting schedule by hand, as it requires quite a complicated work in which various physical and logical constraints have to be considered. S⁴ provides unique functions such as automatic adjustment of shunting time, checking crossover conflicts and others to facilitate shunting scheduling. This paper describes the functions of S⁴ and a Shunting Scheduling Network, we have introduced to realize the functions of S⁴.