Suppressing secondary shock waves in jam-absorption driving via string-stable support vehicles

TL;DR

This paper introduces a control method using connected and automated support vehicles to suppress secondary shock waves in jam-absorption driving, improving traffic stability and safety.

Contribution

It proposes a string-stability-based control strategy for support vehicles to enhance jam-absorption driving and prevent secondary shock waves.

Findings

SD damped perturbations caused by the absorbing vehicle

Combining JAD and SD reduced fuel consumption and collision risk

Reverting time gaps maintained low collision risk with increased travel time

Abstract

As a freeway-driving strategy, jam-absorption driving (JAD) clears a traffic shock wave (stop-and-go wave) by slowing down a single vehicle, called the absorbing vehicle. However, JAD may destabilize the traffic flow upstream of this vehicle, generating secondary shock waves. This study proposes a method to suppress secondary shock waves by controlling the behavior of connected and automated vehicles (CAVs) upstream of the absorbing vehicle, called support vehicles (SVs). A string-stability-based control method is applied in which SVs dynamically extend their time gaps to provide support driving (SD) for JAD. Numerical simulations revealed that SD damped perturbations caused by the absorbing vehicle and prevented secondary shock waves, consistent with the head-to-tail string stability criterion. Combining JAD and SD reduced fuel consumption and collision risk compared with the JAD-only method, but increased travel time. Reverting the extended time gap to its initial value reduced travel time while maintaining low collision risk compared with the non-reverting method, albeit with increased fuel consumption. Thus, combining JAD and SD effectively eliminates the target shock wave while suppressing secondary shock waves with guaranteed string stability.