Multiple pickup and delivery TSP with LIFO and distance constraints: A VNS approach

Abstract

The pickup and delivery traveling salesman problem with last-in-first-out loading (TSPPDL) requires that a set of pickup and delivery requests are fulfilled such that the items to be transported are loaded in LIFO order. We generalize the TSPPDL to consider multiple vehicles as well as a maximum distance constraint for each vehicle; a solution to this problem is a set of routes for each vehicle, and each route can be represented by a tree data structure. To solve this problem practically, we propose a variable neighborhood search (VNS) heuristic using several new search operators. Our VNS approach also includes a dynamic programming component for optimally solving TSPPDL instances. © 2011 Springer-Verlag.