To build on Charlie’s comments, the main driver behind car scheduling in TCS was the trip plan. When a car was released for movement, TCS developed a trip plan for that car from origin to destination. It would take into account the day and time released and determine the first job available to move the car and then determine each subsequent move based on the schedule of the previous train or yard job. Determining the scheduling for each potential move would seem to be the biggest issue in creating the program.