ABSTRACT
Railway networks are ubiquitous in today’s world, and they continue to play a dominant role in transporting freight and people since 1825, when the first common carrier railroad was introduced. While larger countries such as the United States, Russia, China, India, and the EEC benefit most from extensive and cost-effective railway networks, in many smaller but densely populated countries with large financial resources such as Japan, railway networks contribute significantly to the well being of the national economy by efficiently moving workers and goods. As of 1987, the United States [33] maintains a total of 249,412 miles of railway tracks. It supports a total of 1,249,075,534 locomotive unit miles in one year to carry freight utilizing 5,989,522 loaded cars. For passenger services, the total unit miles stands at 3,782,470 while carrying the gross ton-miles of 1,357,097. In Japan, the East Japan Railway Company (Ryuji Sakamoto, pers. comm., December 1987) carries a total of 16million passengers each day on 12,000 scheduled trains and 7,500 km of railway track. For efficiency, modularity, and safety, in general, the tracks are divided into individual units, each of which may be controlled exclusively by the system. Thus, a train in propagating from a location A to another location B may travel over several tracks. Given that two or more trains may compete at some time instant for the same track, and that only one train may occupy a track at any time, the principal goal of the railway network management system is to allocate tracks to trains such that (1) collisions are avoided and (2) the resources are optimally utilized.
