| In a transportation relay network, shipments are transported through a physical network from origin to destination via a system of intermediate relay or transfer points. Only at these intermediate points can shipments be transferred from one vehicle to another, crews be changed, etc.; Examples of transportation relay networks include the postal systems of many ancient civilizations, the Pony Express, less-than-truckload networks, and modern intermodal operations. Some of the benefits of relay networks include greater service possibilities, faster service, and efficient use of vehicles and crews. The relay network class includes almost all transportation and distribution systems in use today. Since a relay network provides a global model (rather than an individual piece) of a transportation system, it is a powerful modeling tool.; In longhaul truckload operations, a relay network is used to return drivers home frequently. Since the trucking industry is facing a driver shortage, the primary advantage of this is better working conditions for drivers which results in improved driver retention for an individual company. In addition, a relay network has several other advantages over current point-to-point solutions for longhaul truckload operations, including decreasing delivery time, increasing equipment utilization, and identifying geographic imbalances. This work provides the first algorithmic approach for designing a relay network for a truckload company, including the introduction of a special multi-commodity flow problem for balancing flows across a network, the development of a general purpose heuristic, the Spring Algorithm, used to consolidate locations on a network while retaining distance constraints, and an algorithm for assigning drivers to locations. |
