A HUMP SEQUENCING ALGORITHM FOR REAL TIME MANAGEMENT OF TRAIN CONNECTION RELIABILITY

This paper describes the hump sequencing component of the Terminal Priority Movement Planner (TPMP), a proof-of-concept decision support system field tested in 1994 at Union Pacific Railroad's Hinkle, Oregon, classification yard. The aim was not to make all connections, but to ensure that at least a subset of the most important ones--those which would cause late deliveries if missed--were protected. Rather than automatically dropping late connections, TPMP minimizes delays associated with holding outbound trains as necessary to protect connections. When called for, the decision to drop a late inbound connection and leave cars behind is made by a human being, not a computer. A mixed integer, nonlinear mathematical programming problem is solved using breadth-first branch and bound search. Realistic 1-day problems are solved in 15-20 sec. on a microcomputer. Practical adaptations required to implement the procedure in a real world setting are also described. Considerable emphasis is given to discussion of factors affecting rail service reliability, and steps railroad management can take to improve performance.