MICROSTRUCTURE AND MICRODYNAMICS OF UNINTERRUPTED TRAFFIC FLOW

In this paper, ''uninterrupted homogeneous traffic flow'' is viewed as a dynamic system of spontaneously aggregating and breaking clusters o f cars. This approach gives qualitative and quantitative descriptions of density fluctuations and dynamics of free traffic flow in terms of car clusters, and their distributions with respect to the number of ca rs in a cluster. The distributions have a nontrivial shape and a nonli near dependence on the density of cars on the expressway. Their shape and evolution as a function of car density are described adequately by a model proposed here. This one-parameter model based on a modified S moluchowski equation predicts a critical density at which a phase tran sition occurs from free to synchronized traffic how for a multilane ex pressway: rho(cr)=16+/-3 vehicles km(-1) (lane)(-1), and that below th is critical density traffic flow can be treated as a one-dimensional s ystem. The model may also find application in the study of the low den sity pneumatic transport of granular and powdered materials.