From Microscopic to Macroscopic Traffic Models
  The paper presents a systematic derivation of macroscopic equations for freeway traffic flow from an Enskog-like kinetic approach. The resulting fluid-dynamic traffic equations for the spatial density, average velocity, and velocity variance of vehicles are compared to equations, which can be obtained from a microscopic force model of individual vehicle motion. Simulation results of the models are confronted with empirical traffic data. 
Dirk Helbing