The Phase Diagram of Congested Traffic States

Abstract

In the previous chapter, we characterized the stability properties of traffic flow models by stability diagrams of steady-state traffic as a function of density, and by stability classes distinguishing the most relevant qualitative features of the stability diagrams. Now, we show how this determines the spatiotemporal dynamics of congestion patterns in realistic open systems with bottlenecks. Besides the stability class, the influencing factors are the traffic demand, and the bottleneck strength. We discriminate qualitatively different patterns by regions in a dynamic phase diagram spanned by traffic demand and bottleneck strength and compare the theoretical result with simulated and real congestions. It turns out that the observations are described by stability classes displaying instabilities for congested traffic, only.