This article presents a method to uncover universal patterns and similarities in the urban road networks of the 80 most populated cities in the world. To that end, we used degree distribution, link length distribution, and intersection angle distribution as topological and geometric properties of road networks. Moreover, we used ISOMAP, a nonlinear dimension reduction technique, to better express variations across cities, and we used K-means to cluster cities. Overall, we uncovered one universal pattern between the number of nodes and links across all cities and identified five classes of cities. Gridiron Cities tend to have many 90° angles. Long Link Cities have a disproportionately high number of long links and include mostly Chinese cities that developed towards the end of the 20th century. Organic Cities tend to have short links and more non-90 and 180° angles; they also include relatively more historical cities. Hybrid Cities tend to have both short and long links; they include cities that evolved both historically and recently. Finally, Mixed Cities exhibit features from all other classes. These findings can help transport planners and policymakers identify peer cities that share similar characteristics and use their characteristics to craft tailored transport policies. @en

Transportation systems are the lifeblood of countries and cities, supporting mobility for people, goods exchange, and businesses connectivity. The efficient and sustainable performance of these systems is crucial in all urban, rural, and in between spaces, not least for emergency management (e.g., evacuation, rescue, and recovery). Urban transportation systems (UTSs) are under increasing pressure due to increase of demand, aging and deterioration, and the impacts from weather-related hazards. These hazards can be very disruptive for transportation systems, both at financial and societal level. The focus of this chapter is on safety of UTSs. After a general overview of all major impacts to UTSs due to natural and man-made hazards, the chapter emphasizes how roadway conditions are influenced by a variety of adverse weather events (e.g., snow, rain, heat, and windstorm) in terms of safety, service delivery, and accessibility. This chapter also provides the thresholds of adverse weather events that can impact roadway conditions in different countries around the world to give the readers a better understanding of geographical location importance in the context of road safety. This chapter will also introduce three international case studies within transportation networks, putting them in the wider context of traditional approaches to study these systems. The topic is discussed by underlining multi-disciplinary cross-cutting issues to invite the reader to personal reflection and creative thinking.

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