🎓 Ph.D. Thesis by Luis Guillermo Natera Orozco
With more than half of the world's population living in cities, it is fundamentally important to understand how the complex system of urban mobility infrastructure, from sidewalks and bicycle paths to streets and rails, shapes and modifies human mobility. In this thesis, we use network science to study cities and their mobility infrastructures. We treat these infrastructures as layers of a multiplex network, such as sidewalks, bicycle paths, subway systems and streets, and develop and apply network science based tools to study these layers both individually and jointly. First, we survey the existing literature of cities as multiplex networks, from infrastructure and dynamics to existing measures, data and analysis tools. Second, we propose a new method to extract the multimodal profile from a city's multiplex transport network. We show how this method can be applied to identify multimodal similarities between cities. Third, we focus on the bicycle layer of the multimodal network, investigate its structure, and find that it consists of hundreds of disconnected patches. To connect these patches, we develop and apply data-driven, algorithmic network growth strategies, showing that small but focused investments allow to significantly increase the connectedness and directness of urban bicycle networks. In the fourth chapter, we present a data-driven, network-based method to quantify the livability of a city, computing pedestrian accessibility to amenities and services, taking into consideration safety and environmental variables. Finally, we discuss the main contributions of this thesis and outline possible applications and open questions for the future. We anticipate that this work contributes directly to the understanding of urban systems providing new insights and tools for the evaluation of sustainable urban mobility infrastructures. Understanding, improving, and evaluating urban mobility infrastructures are major steps for improving urban life and to plan ahead of climate change, thus a well-defined set of tools and metrics will be relevant to move forward.