Pickup and delivery problem with time windows: A new compact two-index formulation

We propose a formulation for the pickup and delivery problem with time windows, based on a novel modeling strategy that allows the assignment of vehicles to routes explicitly in two-index flow formulations. It leads to an effective compact formulation that can benefit OR practitioners interested in solving the problem by general-purpose optimization software. Computational experiments indicate that the proposed formulation has interesting features and best overall performance in relation to other compact formulations.