Abstract

Scheduling the switching engines of an industrial railroad is a formidable and responsible task, closely related to the well-studied pickup and delivery problem with time windows. Aiming at an efficient usage of resources the need arose for a computer aided scheduling tool as support for the human dispatcher. We sketch a set partitioning formulation of this problem to be solved via column generation. The pricing subproblem is hard in the theoretical sense but can be solved by means of a combination of heuristics and exact algorithms. A trade-off between mathematical rigor and practicability becomes apparent and is extensively discussed. Our computational experience with an academic prototype implementation is encouraging. We succeed in obtaining practically acceptable solutions for instances of more than forty customers and six vehicles.

Citations