Hierarchical Location-Allocation Models for Congested Systems

In this paper we address the issue of locating hierarchical facilities in the presence of congestion. Two hierarchical models are presented, where requests are attended first by lower level servers, and then some of the served customers are referred to higher level servers. In the first model, the objective is to find the minimum number of servers and locations that will cover a given region within given distance or time limits. The second model is cast as a Maximal Covering Location formulation. A heuristic procedure is then presented together with computational experience Finally, some extensions of these models are put forward addressing other types of spatial configurations