Multi-Layer Network Design for Consolidation-Based Transportation Planning

Multilayered networks are used to model systems with multiple interacting components, each being represented by a network layer. More than two layers may be involved. The Operations Research multi-layer network term is generally associated with complex multilayered problem settings, frequently encountered in planning transportation and telecommunication systems, where an arc in a given layer is defined with respect to a set of arcs in another layer. Multi-layer network design aims to simultaneously design all layer-specific networks to satisfy at minimum overall cost a given set of origin-destination demands. Extending the already-difficult network design problem class, multi-layer network design presents additional modelling and algorithmic challenges arising from the connectivity relations and requirements characterizing the design, flow, and attribute decision variables associated with the arcs of interconnected layers. We recall and enhance the basic definitions and formulations, and introduce new ones for richer multi-layer networks, with more than two layers and connectivity relations involving several layers simultaneously. We illustrate these concepts through multi-layer service network design models for tactical planning of consolidation-based freight transportation carriers.