Statistical Physics of Synchronized Traffic Flow: Spatiotemporal Competition between S$\to$F and S$\to$J Instabilities

Abstract

We have revealed statistical physics of synchronized traffic flow that is governed by a spatiotemporal competition between S$\rightarrow$F and S$\rightarrow$J instabilities (where F, S, and J denote, respectively, the free flow, synchronized flow, and wide moving jam traffic phases). A probabilistic analysis of synchronized flow based on simulations of a cellular automaton model in the framework of three-phase traffic theory is made. This probabilistic analysis shows that there is a finite range of the initial space-gap between vehicles in synchronized flow within which during a chosen time for traffic observation either synchronized flow persists with probability $P_{\rm S}$, or an S$\rightarrow$F transition occurs with probability $P_{\rm SF}$, or else an S$\rightarrow$J transition occurs with probability $P_{\rm SJ}$. Space-gap dependencies of the probabilities $P_{\rm S}$, $P_{\rm SF}$, and $P_{\rm SJ}$ have been found. The statistical features of synchronized flow found for a homogeneous road remain qualitatively for a road with a bottleneck. However, rather than nuclei for S$\rightarrow$F and S$\rightarrow$J instabilities occur at random road locations of the homogeneous road, due to a permanent non-homogeneity introduced by the bottleneck, nuclei for initial S$\rightarrow$F and S$\rightarrow$J instabilities appear mostly at the bottleneck.