  This paper considers mixed traffic consisting of connected automated vehicles
equipped with vehicle-to-everything (V2X) connectivity and human-driven
vehicles. A control strategy is proposed for communicating pairs of connected
automated vehicles, where the two vehicles regulate their longitudinal motion
by responding to each other, and, at the same time, stabilize the human-driven
traffic between them. Stability analysis is conducted to find stabilizing
controllers, and simulations are used to show the efficacy of the proposed
approach. The impact of the penetration of connectivity and automation on the
string stability of traffic is quantified. It is shown that, even with moderate
penetration, connected automated vehicle pairs executing the proposed
controllers achieve significant benefits compared to when these vehicles are
disconnected and controlled independently.
