Application of the Network Robustness Index to Identify Critical Links Supporting Vermont's Bulk Milk Transportation

摘要

The food supply chain is an interwoven network consisting of producers, processors, manufacturers, distributors, retailers, and consumers. With the exception of direct marketing or community-supported agriculture systems, some or all of these intermediaries are involved. In all cases, links between each member of the supply chain are subject to disruption. A disruption in transit of goods between any of these points, be it a detour, poor road condition, theft, accident, or major disruption caused by natural, accidental, or intentional catastrophe can have consequences ranging from reduced efficiency of operations to total loss of value of product (if stolen or highly perishable). Given that the food and agriculture sector was declared a critical infrastructure by Homeland Security Presidential Directive 9, ways to assess vulnerabilities and prioritize mitigation strategies are needed. One such tool for identifying critical links in a transportation network is the Network Robustness Index (NRI). The NRI provides a system-wide approach to identifying critical links and evaluating transportation network performance. The theoretical framework of the NRI accounts for network-wide demand and traffic re-assignment. It may prove a useful approach for evaluating critical links for freight commodity or any other transportation flows. The objective of this project was to apply the NRI to a real-life data set of freight transportation flows over a real road network. Given the dominant position of dairy in Vermont's agricultural production and export markets, the flow of bulk milk from farm to first collection point was selected for study. Application of the NRI to Vermont milk transportation networks would help focus attention on links critical to the overall performance of the road infrastructure serving the raw milk supply chain. This report presents the analysis of a data set reflecting milk movements in northwestern Vermont.