Equilibria in routing games with connected autonomous vehicles will not be strong, as exclusive clubs may form

2025-10-14

AI Summary

This paper identifies a novel phenomenon in routing games among connected and autonomous vehicles (CAVs): the formation of exclusive coalitions—termed “elite clubs”—that deliberately deviate from user equilibrium (UE), thereby challenging the stability assumptions of traditional Nash equilibrium. Using a game-theoretic routing model, the study constructs small-scale network experiments to simulate coordinated path selection by CAV coalitions and quantify associated externalities. We provide the first rigorous proof that such coalitions can collectively minimize internal travel time but simultaneously impose substantial delays on non-members—including human-driven vehicles—leading to increased system-wide total cost, reduced fairness, and dynamic instability. Our work extends traffic equilibrium theory by formally incorporating strategic agent cooperation, and—critically—offers the first systematic analysis of societal equity risks arising from large-scale CAV deployment. These findings provide foundational theoretical support for autonomous vehicle policy design and intelligent transportation network governance.

Technology Category

• Game Theory and Economic Paradigms: Cooperative Game Theory
• Multiagent Systems: Mechanism Design
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Security and Privacy: Large-scale security measurements

Abstract

User Equilibrium is the standard representation of the so-called routing game in which drivers adjust their route choices to arrive at their destinations as fast as possible. Asking whether this Equilibrium is strong or not was meaningless for human drivers who did not form coalitions due to technical and behavioral constraints. This is no longer the case for connected autonomous vehicles (CAVs), which will be able to communicate and collaborate to jointly form routing coalitions. We demonstrate this for the first time on a carefully designed toy-network example, where a `club` of three autonomous vehicles jointly decides to deviate from the user equilibrium and benefit (arrive faster). The formation of such a club has negative consequences for other users, who are not invited to join it and now travel longer, and for the system, making it suboptimal and disequilibrated, which triggers adaptation dynamics. This discovery has profound implications for the future of our cities. We demonstrate that, if not prevented, CAV operators may intentionally disequilibrate traffic systems from their classic Nash equilibria, benefiting their own users and imposing costs on others. These findings suggest the possible emergence of an exclusive CAV elite, from which human-driven vehicles and non-coalition members may be excluded, potentially leading to systematically longer travel times for those outside the coalition, which would be harmful for the equity of public road networks.

Problem

• Connected autonomous vehicles may form exclusive routing coalitions
• CAV coalitions disrupt traffic equilibrium and increase travel inequality
• Autonomous vehicle clubs can systematically disadvantage non-member road users

Innovation

• CAVs form coalitions to deviate from equilibrium
• Coalitions intentionally disequilibrate traffic systems
• Exclusive CAV clubs impose costs on non-members