1. In a railroad system wherein a plurality of trains is operated over multiple interconnected tracks, a traffic-control system comprising the following combination of components: (a) means for assigning a travel schedule to each of a plurality of said trains and for storing said schedule in a computer memory; (b) means for determining each train's position as the train progresses along said tracks; (c) means for comparing said train's position with said travel schedule assigned thereto to produce a compliance indicator indicative of a schedule variation for the train; (d) means for calculating, when said schedule variation exceeds a predetermined acceptable threshold, an alternative travel schedule for each of said plurality of trains as necessary to maintain predetermined operating parameters within the system; and (e) means for automatically changing said travel schedule of each train in the computer memory to conform prospectively with said alternative travel schedule.