International trade continues to grow, increasing container traffic at seaports worldwide. Typically, loaded containers arriving at the ports are transported by truck to inland importers, emptied, and then returned to the port. The empty containers are then driven to inland exporters to be loaded and returned to the port for shipping. This lack of direct container exchange between importers and exporters, known as the empty container reuse problem, adds many truck trips to Southern California highways and adds significant expenses for shipping companies. Trucks transporting empty containers contribute to traffic congestion, greenhouse gas emissions, and local air pollution.
Moving empty containers more efficiently could significantly reduce truck trips and the associated congestion and pollution. Researchers at the University of Southern California developed an optimization-based vehicle scheduling model that allows for a “street exchange” in which empty containers can go directly from importers to exporters without returning to the port. The model satisfies the current day’s known, or deterministic, demand while also accounting for the next day’s unpredictable, or stochastic, demand. The model is solved iteratively each day using this two-day time horizon to provide a routing plan for the current day’s demand. The model was tested using container demand data from the Ports of Los Angeles and Long Beach as well as randomly generated data sets. This research brief summarizes findings from that project.