Relay network design with direct shipment and multi-relay assignment

The truckload industry faces a serious problem of high driver shortage and turnover rate, typically around 100%. Among the major causes of this problem are extended on-the-road times, where drivers handle several truckload pickup and deliveries successively, non-regular schedules and get-home rates, and low utilization of drivers dedicated time. These are by-and-large consequences of the driver-to-load dispatching method, which is based on point-to-point dispatching or direct shipment from origin to destination, commonly employed in the industry. Use of relay networks has been suggested previously to alleviate this problem, mainly due to its underlying causes. In this scheme, a truckload on its way to destination visits multiple relay nodes (each representing a service region) and its driver and/or tractor are exchanged with a new one serving the next relay so that drivers stay close to their home domiciles. In this study, we consider a generalized relay network design problem whose specific design characteristics include the possibility of both direct and relay-network shipments and multi-route assignments in addition to fixed relay costs and control of route circuity levels. We present a new MILP model capturing these characteristics effectively and solve it effectively by Benders decomposition. The solution approach helps us to further examine the performance of the relay network under generalizing characteristics and quantify the improvements in practice when direct shipments and multi-assignment are employed. Computational study demonstrates the performance of the algorithm and include further analysis of results. In general, relay networks also find applications in transportation with alternative fuels, e.g., charging locations in long distance electric vehicle transportation networks, and in communication networks, e.g., signal regeneration facilities in long-distance data networks.