Exploring Traffic Paradoxes: A Study of Roundabout Corridors and Their Effects on Network Dynamics

This research is part of a broader investigation into dynamic simulation-based approaches for enhancing traffic efficiency, road safety, and sustainability in roundabout corridors and/or road corridors in general. The study emphasizes the need to analyze road intersections as interconnected systems rather than isolated components, aiming to better understand and mitigate counterintuitive phenomena known as traffic paradoxes, including the well-known Braess Paradox. The first section introduces the main traffic paradoxes, exploring their definitions, real-world implications, and reproducibility in roundabout corridors. The second section focuses on a case study of the “SS1—Via Aurelia Nord” in Pisa (Italy), where converting a traffic-light-controlled corridor into a roundabout corridor unexpectedly led to increased congestion. This paradoxical outcome is analyzed within the broader context of network dynamics and sustainable mobility planning. Dynamic simulations were performed using Aimsun software, and a novel performance index—the “Celerity Roundabout Corridors” (CRC)—was proposed to quantify and detect these paradoxical effects. The findings highlight conditions under which roundabout corridors may generate inefficiencies despite infrastructural upgrades, emphasizing the importance of systemic, simulation-based evaluations for the sustainable design and optimization of urban traffic networks.