Event-triggered Varying Speed Limit Control of Stop-and-go Traffic

Espitia, Nicolás; Yu, Huan; Krstić, Miroslav · 2020 · IFAC-PapersOnLine

DOI: 10.1016/j.ifacol.2020.12.1343

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Summary

This paper addresses the challenge of suppressing stop-and-go traffic oscillations on congested freeways using event-triggered varying speed limit (VSL) control. The authors are motivated by the practical limitations of continuous-time control strategies, which are difficult to implement on digital platforms and may cause unsafe driving conditions due to frequent speed advisory updates. By adopting an event-triggered approach, the control signal is updated only when necessary, reducing computational and communication resource usage while providing drivers with adequate adaptation time. The study models traffic dynamics using the linearized Aw-Rascle-Zhang (ARZ) macroscopic partial differential equation (PDE), which describes traffic density and velocity as a $2 \times 2$ coupled hyperbolic system. The control strategy regulates the velocity of vehicles leaving a freeway segment via a VSL at the outlet. The authors employ a full-state backstepping boundary feedback design, transforming the system into a stable target system. To implement this digitally, they propose two Lyapunov-based event-triggered strategies that determine when the control value must be sampled and updated. The first strategy uses a static triggering condition with time regularization to enforce a minimum inter-event time, thereby avoiding the Zeno phenomenon (infinite triggering in finite time). The second strategy employs a dynamic triggering condition, which introduces an auxiliary dynamic variable to filter the triggering signal, allowing for fewer updates while guaranteeing a uniform minimal dwell-time independent of initial conditions. The main results establish the exponential stability of the closed-loop system under both event-triggered strategies. The authors prove that the static strategy avoids Zeno behavior through enforced waiting times, while the dynamic strategy ensures a minimal dwell-time without explicit time regularization. Numerical simulations validate these findings using a 1 km freeway segment with congested initial conditions. The results demonstrate that both strategies successfully suppress traffic oscillations. Notably, the dynamic triggering condition reduces the number of control updates compared to the static approach, offering a more efficient implementation for digital VSL systems. The study confirms that event-triggered control provides a realistic and stable method for managing freeway congestion, balancing performance with practical implementation constraints.

Key finding

Event-triggered boundary control strategies based on the linearized Aw-Rascle-Zhang model successfully stabilize stop-and-go traffic oscillations while reducing unnecessary control updates compared to continuous or periodic methods.

Methodology

simulation_modeling

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• speed management