Event-Triggered Control of Freeway Traffic Flow with Connected and Automated Vehicles

We propose an event-triggered control (ETC) strategy for the Aw-Rascle-Zhang (ARZ) traffic model under congested conditions. The considered ARZ-type model, governed by first-order hyperbolic partial differential equations (PDEs), captures traffic dynamics involving both Adaptive Cruise Control (ACC) and human-driven vehicles. Control actions adjust the time gap for ACC vehicles and are updated based on a suitable triggering rule. We conduct the stability analysis on a linearized and transformed system (a 2×2 linear hyperbolic system with in-domain control), and we asses input-to-state stability (ISS) with respect to actuation errors. A small-gain approach guides the design of appropriate triggering rule (small-gain event based triggering condition), ensuring exponential stability while preventing the Zeno phenomenon. Numerical simulations demonstrate the effectiveness of the proposed control strategy in stabilizing traffic flow.