Estimating the Capacity of Freight Transportation Systems: A Model and Its Application in Transport Planning and Logistics

The issue of adequate capacity in the freight transportation system to accommodate growing cargo volumes is now becoming a major public policy concern. The problem of extraordinary rail line congestion and service failures in connection with the recent Union Pacific–Southern Pacific merger has galvanized attention to the problem, but the issue extends far beyond the rail system to other modes and contexts. The concept of system capacity (as opposed to link or facility capacity) is developed, and prior literature is reviewed for approaches to estimating it. A model that was developed from the most promising of these is presented. This model is multimodal in concept and is intended to be applicable to any vehicular freight mode. The model is tested through application to a portion of the rail network, and results are assessed for reasonableness and utility. Finally, the applicability of the model and approach to various capacity-related questions is described and discussed.