ESTIMATING THE CAPACITY OF TRANSPORTATION SYSTEMS: A MODEL WITH APPLICATIONS TO FREIGHT TRANSPORTATION

The issue of adequate capacity in the freight transportation system to accommodate growing cargo volumes is now becoming a major public policy concern. While the problem of extraordinary rail line congestion and service failures in connection with the recent UP-SP merger has galvanized attention to the problem, the issue extends far beyond the rail system to other modes and contexts. In this paper, the concept of system capacity (as opposed to link or facility capacity) is developed, and prior literature reviewed for approaches to estimating it. A model which is developed from the most promising of these is presented. This model is multi-modal 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 assessed for reasonableness and utility. Finally the applicability of the model and approach to various capacity-related questions is described and discussed.