Introducing the platoon fundamental diagram for automated vehicles based on large-scale empirical observations

Abstract

The interest in understanding the coordinated behavior of car-platoons and their impact on traffic efficiency, safety and energy demand is high. Recently, real-world experiments towards observing car-platoons with ACC-driven vehicles became available. Literature highlights that such car-platoons are string unstable, energy inefficient and potentially safety critical. However, few studies link their behavior at microscopic level to the macroscopic impact on traffic. In this paper, we propose a novel model, namely the Platoon Fundamental Diagram (PFD), that creates explicitly such a link. We validate PFD through worldwide experimental observations and we show that PFD can be reliably used as a means of cross-comparison between platoons with automated vehicles. Furthermore, we present evidence about the invariability of PFD to heterogeneity, i.e. the number of vehicles in the platoon, the order of vehicles, the vehicles' powertrains, the vehicle brands or models within the car- platoon, the particularities of the road infrastructure and the data acquisition methods.