Analysis of freight transportation network redundancy: An application to Utah's bi-modal network for transporting coal

Freight transportation network is an essential backbone for supporting the industrial activities and economic developments of the nation and global trade. In this paper, we extend the network-based measures recently developed by Xu et al. (2018) for assessing freight transportation network redundancy – an important component in making freight transportation networks more robust and resilient against disruptions. Redundancy of freight transportation networks is characterized by two network-based measures. The route diversity measure evaluates the existence of multiple efficient routes available for freight users or the degree of connections between a specific origin-destination (O-D) pair, while the network spare capacity measure quantifies the network-wide spare capacity with an explicit consideration of congestion effect and modal split. These two measures can complement each other by providing a two-dimensional characterization of freight transportation network redundancy that can be used to provide information to freight users as well as to assist network planners in making future infrastructure investment decisions to enhance the redundancy of freight transportation networks. A case study of the Utah freight network for transporting coal is provided to demonstrate the features of the two network-based redundancy measures as well as the applicability of assessing the redundancy of freight transportation networks. The analyses reveal that the two measures provide useful results from two perspectives that may be of benefit to freight carriers and transportation system planners.