Unveiling the Influence of Automated Vehicles on the Fundamental Diagram: Adaptive Cruise Control

Abstract: Automated vehicles (AVs) have been highly anticipated due to their potential to reduce congestion. The first generation of AVs using Adaptive Cruise Control (ACC) has become commercially available in recent years. Understanding the fundamental traffic flow characteristics for those automated vehicles is critical for the future of traffic operations and planning as Adaptive Cruise Control (ACC) market penetration increases. To provide a better understanding of traffic flow characteristics for commercially available Adaptive Cruise Control (ACC), this study conducted microscopic simulations using a well-designed ACC car-following model validated by a comprehensive set of full-speed range car-following field experiments. Varying ACC market penetration rates were tested, and the fundamental diagrams for each penetration level were developed. This study addresses the previous gap in research, which relied on either speculative simulations or field data from a few vehicles to generate the fundamental diagram. Findings of this study show that as ACC market penetration increases, the capacity and jam density significantly decrease, to as low as 1500 veh/hr/ln and 60 veh/km, respectively, at 100% market penetration. Also, the wave speed increases significantly as market penetration increases and the shape of the diagram becomes nonlinear at higher market penetrations, due to the sharp decrease in jam density.