A non-triangular hub location problem

Abstract

Hub location problems generally assume that the triangle inequality applies on the edges of a complete graph. Hence the flow between any pair of nodes requires at most two hubs for the transfer process. Here we relax the triangle inequality restriction and present two new formulations of the uncapacitated multiple allocation p-hub median problem that allow transfer through more than two hubs. Some testing is performed on newly generated instances where the triangle inequality does not hold in order to assess the tractability of these new mathematical models, and their usefulness compared to the standard approach.