Scheduling Freight Trains in Rail-Rail Transshipment Yards

Transshipment yards, where gantry cranes enable the efficient transfer of containers between freight trains, are important entities in modern railway systems. They facilitate a general shift from point-to-point transport to hub-and-spoke railway systems, a shift being driven by concerted efforts within the European Union (EU) to transfer goods traffic from road to rail. Modern rail-rail transshipment yards accelerate container handling so that multiple smaller trains, with identical destinations, can be consolidated onto a reduced number of trains. An important problem attendant upon the daily operations of a transshipment yard is the train-scheduling problem, which involves determining the processing order of trains at parallel railway tracks. The present paper investigates this problem, with a special focus on resolving deadlocks and avoiding multiple crane picks per container move. A mathematical program along with a complexity proof is provided, and two different procedures are described: exact (dynamic programming) and heuristic (beam search).