Modeling Freight Network Robustness and Criticality in Ontario, Canada

This dissertation explores criticalities that arise in a freight transportation network for the multi-regional economically active province of Ontario, Canada. A significant economic contributor and generator of freight trips, Ontario relies on its transportation system for the movement of goods. A combination of network performance and economically driven measures are used to evaluate the impacts of link disruptions, identify criticalities in the network, and produce a more holistic view of freight transportation activities. The Network Robustness Index (NRI) is applied to capture the impacts of travel conditions on the network due to link disruptions. A methodology is introduced for estimating industry-level freight demand and shipment value flows to ascertain the economic importance at the link-level. Major trade routes, including the Montreal-Windsor corridor along Highway 401 and highways leading to major border crossings with the United States, as well as highways in the Toronto region and links to northern Ontario consistently appear critical in the analysis. In combination, these measures are useful for developing a framework for assessing the effectiveness of proposed infrastructure improvements in mitigating the impacts of critical link failures. The first chapter of the research presented in this thesis is dedicated to evaluating the effectiveness of the NRI to capture the impacts of link disruptions with respect to freight activity. Chapter 2 employs a sensitivity analysis to explore the network-wide impacts of increasing degrees of disruption on six segments deemed critical due to their frequency of use as part of shortest-path routes between origins and destinations. While the most severe impacts are noted closer to the disrupted network segments, complete link failures or closures along heavily traveled routes appear to have significant impacts through the network as freight and passenger flows must reroute. To better capture the nature of freight activity for the entire province of Ontario, Chapter 3 applies the NRI to each of the network’s 35,254 links, simulating traffic assignments for the province’s freight demand to note the impact that each link’s failure has on network conditions. Chapter 4 adds the economic perspective by introducing a methodology for disaggregating freight flows into six mutually exclusive industry categories, following the assumption that spatial interactions will vary among different industries due to the nature of the goods carried and their respective markets. Additionally, the average shipment value is estimated for each industry group to illustrate the eco nomic importance of network links, given by the value of goods they carry. This analysis allows for a better understanding of the economic activities of freight being undertaken in the province. A set of highly critical portions of the network are highlighted consistently. Finally, these measures are brought together in a framework, where network criticalities are compared to the locations of proposed infrastructure improvements. A comparison is made among four highway expansion segments planned along highly critical portions of the network, evaluating the resulting impacts of these improvements with respect to operating conditions on the network, economic throughput, and greenhouse gas emissions. Each chapter of this research proposes policy guidelines meant to identify network criticalities, mitigate the negative impacts of critical link failures, and compare the effects of proposed infrastructure improvements and investments. The goal of these policy guidelines is to ensure that the maximum benefit is achieved, both in terms of network conditions, as well as with respect to promoting economic productivity.

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