Four-phase Infrastructure Resilience Cycle Framework for Urban Multimodal Public Transportation Networks

四階段基礎設施韌性週期框架用以分析城市多模式公共交通網絡

Student thesis: Doctoral Thesis

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Award date2 Sep 2022

Abstract

Resilience emerges as a hot topic in the fields of urban infrastructure and climate change adaptation due to the imperative requirement of a systematic approach to resilience engineering. Traditional risk management shows limitations in assessing long-term and complex infrastructures when facing unpredictable future threats. In the decision-making process, the system interconnection and interdependence increase the difficulty and solution size for risk management, while resilience is the new strategy that highlights graceful degradation and adaptation instead of prevention.

This thesis evaluates urban public transportation networks (PTNs) with a network-based resilience cycle quantification framework that is developed based on the four-phase life cycle concept (i.e., plan/prepare, absorb, recover, and adapt) and the knowledge from network science. We aim to explore the impact of the demand flow, system capacity, organization manner, system interconnection, and system (inter)dependence in the resilience assessment. Network analysis, from network science, provides a top-down approach to revealing system resilience with its advantage in dealing with the high complexity and large system scale. It draws a grand picture of system-level resilience in the face of natural and human-made hazards.

Case studies are conducted in chapters for PTNs from Hong Kong and other cities, with the modes of transportation varying from the metro to bus, ferry, light rail, and tram. We demonstrate the utility of the network-based resilience cycle framework by quantitatively comparing metro systems from five different cities. Different phases of the resilience cycle show trade-offs, meaning that a single metric cannot measure resilience. As for our core topic, the multimodal PTN is evaluated as an interconnected system, which displays better resilience than isolated systems. Enhancing intermodal transfer is found to be an effective way to improve the resilience of existing PTNs. Besides, the system dependency results in new exposure to failures, bringing new vulnerabilities to a system and changing the response type. In the Hong Kong franchised bus case study, rerouting shows very limited effect during large-scale disruptions due to the disintegration of the road system. Additionally, considering flows on the top of the system topology captures both resilience of the system and the users. The average travel distance of flows is found to be an important factor for resilience, and certain flow patterns can undermine system robustness, leaving the system vulnerable to flow-based attacks.

    Research areas

  • resilience, public transportation, infrastructure, network analysis, complex network, multimodal, interconnected, dependent, flow, capacity, preparedness, robustness, recovery, adaptation, metro, bus