Stratified p-Hub Median and Hub Location Problems: Models and Solution Algorithms

The choice of hub locations is fundamental in various transportation and communication systems, enabling transshipment, sorting, and consolidation functions. Recent research has highlighted the benefits of stratification when searching for hub facilities, taking into account the fact that the demand at each site belongs to different strata, e.g., depending on the type or quality of service the passengers or cargo require. In this study, we propose various instances of the stratified single allocation hub location problems, ranging from simple p-hub median / stratified hub location to extensions concerning direct links as well as node capacities. Moreover, four generalized problems, considering service level requirements, capacitated direct links, multi-modal hub networks, and incomplete network structures are derived from the basic problems. Given that the stratified models become intractable to solve for even medium-sized instances, we also develop a novel neighborhood-search based algorithm. Extensive experiments are performed on representative data sets, confirming the effectiveness and efficiency of our solution techniques. The results also further highlight the significance of stratification in hub-and-spoke networks. Our work complements recent studies on stratified p-hub center / maximal covering problems.