Open Access

Linghang Sun, Yifan Zhang, Cristian Axenie, Margherita Grossi, Anastasios Kouvelas, Michail A. Makridis

• Major cities worldwide experience problems with the performance of their road transportationnetworks, and the continuous increase in traffic demand presents a substantial challenge to theoptimal operation of urban road networks and the efficiency of traffic control strategies. The operation of transportation systems is widely considered to display fragile property, i.e., the loss inperformance increases exponentially with the linearly growing magnitude of disruptions. Meanwhile, the risk engineering community is embracing the novel concept of antifragility, enablingsystems to learn from past events and exhibit improved performance under disruptions of previously unseen magnitudes. In this study, based on established traffic flow theory knowledge,namely the Macroscopic Fundamental Diagram (MFD), we first conduct a rigorous mathematicalanalysis to theoretically prove the fragile nature of road transportation networks. Subsequently,we propose a skewness-based indicator that can be readily applied to cross-compare the degreeof fragilityMajor cities worldwide experience problems with the performance of their road transportationnetworks, and the continuous increase in traffic demand presents a substantial challenge to theoptimal operation of urban road networks and the efficiency of traffic control strategies. The operation of transportation systems is widely considered to display fragile property, i.e., the loss inperformance increases exponentially with the linearly growing magnitude of disruptions. Meanwhile, the risk engineering community is embracing the novel concept of antifragility, enablingsystems to learn from past events and exhibit improved performance under disruptions of previously unseen magnitudes. In this study, based on established traffic flow theory knowledge,namely the Macroscopic Fundamental Diagram (MFD), we first conduct a rigorous mathematicalanalysis to theoretically prove the fragile nature of road transportation networks. Subsequently,we propose a skewness-based indicator that can be readily applied to cross-compare the degreeof fragility for different networks solely dependent on the MFD-related parameters. Finally, weimplement a numerical simulation calibrated with real-world network data to bridge the gapbetween the theoretical proof and the practical operations, with results showing the reinforcingeffect of higher-order statistics and stochasticity on the fragility of the networks. This work aimsto demonstrate the fragile nature of road transportation networks and guide researchers towardsadopting the methods of antifragile design for future networks and traffic control strategies.…