Dr Zizhen Xu

Research Interests

Dr. Zizhen Xu's research interests lie at the intersection of resilience of urban infrastructure systems, climate change adaptation, and sustainability. Specifically, he applies complex network theory to explore the disaster resilience of interconnected and interdependent infrastructure systems, with a particular focus on transportation systems.

Strategic Themes

Sustainability

Research Project

Title: Assessing road infrastructure resilience against extreme weather events and fostering climate change adaptation

Theme: Sustainability

Abstract: 

In the highway sector, resilience studies are under high priority to understand how prepared the current highway network is in the face of future severe weather events and its dependency on the related infrastructures. The proposed project aims to develop a system approach to assess highway resilience in the face of extreme weather events, with integrating geospatial analysis, risk assessment, and network analysis and evaluating potential cascading failure.  

Before conducting a resilience assessment for the nation-wide highway network, we conducted a regional case study for Greater London and surrounding areas. Flooding is selected as the major threat for highway network. Current efforts in data collection and modelling have successfully produced a geographical model and a network model of all classified highways. By intersecting the highway geographical model with the Environment Agency flood risk map, we identified the highway segments where flooding is expected to occur in 1 in 30 years, 100 years, and 1000 years event scenarios and the water depths have been sampled for each scenario. In addition to the highway flooding directly impacting the traffic, we also investigated the indirect impacts of the power-signal-traffic cascade due to inundated power substations as well as the highway visibility and slipperiness effect due to intensive precipitations. These three effects have been integrated into our traffic modelling, which allow estimating the average speed and travel time of the traffics on each of the highway segments. With the modelling, we created maps showing the hotspots with high vulnerability in terms of compromised travel efficiency during flooding events. Since the regional case study has proved the feasibility of our methodology, we are currently working on the next step to expand the research area from Greater London and surrounding areas to nationwide including England and Wales. Expanding the highway network increases the complexity and computational load. Considering that, we change the focus from traffic modelling to macroscopic network analysis, which measures community-level mobility (ability to travel to other places) and accessibility (ability to be accessed from other places) during flooding events. We are also particularly interested in the specific accessibility to critical services such as police station, hospital, and food market from local communities facing flooding events. 

This research aligns with the United Nations Sustainable Development Goals (No.13 Climate Actions and No. 9 Industry, Innovation and Infrastructure). The TRL level is expected to achieve 4 from 2. As of now potential secondments would be with National Highways (severe weather operation) and Atkins Realis (asset degradation modelling under climate change). We acknowledge that National Highways has granted us the access to the HADDMS (now the new GDMS) where historical flooding data are being used for validation in the research.

Biography

Dr. Zizhen Xu is a Marie Skłodowska-Curie Future Roads Fellow at the Department of Engineering at the University of Cambridge. He received his PhD in Transportation Resilience in 2022, his MSc in Energy and Environment in 2019 from City University of Hong Kong, and his BEng in Environmental Engineering from Harbin Institute of Technology at Weihai in 2017. His PhD research focused on the disaster resilience of urban public transportation systems. Prior to joining the University of Cambridge, he worked as a postdoctoral researcher at the School of Energy and Environment at City University of Hong Kong. His recent work includes the resilience of interconnected systems such as multimodal transportation networks and industrial symbiosis networks.