In contemporary traffic flow theory, the distinction between user classes is rarely made. However, the accuracy and the descriptive power of the macroscopic traffic flow models can be improved significantly by separating user – classes and their specific flow characteristics. Additionally, the availability of a realistic multiple user – class traffic flow model enables the automated generation of user – dedicated traffic control policies by means of mathematical optimal control theory. A macroscopic multiple user – class model is derived from mesoscopic principles. In this paper there are analysed such a multiple user – class traffic flow model. Starting point for the analysis of the macroscopic flow model is the user – class specific phase – space density, which can be considered as a generalization of the traditional density. The gas – kinetic equations describing the dynamic of the multiclass Phase – Space Density (MUC - PSD) are governed by various interactions processes, such as accelerations towards a class – specific desired velocity, deceleration caused by vehicle interactions and the influence of lane changing. The gas – kinetic equations serve as the foundation of the proposed macroscopic traffic flow models, describing the dynamic of the class – dependent spatial density, velocity and velocity variance. These relations show competing processes: on the one hand, drivers accelerate towards their class – dependent desired velocity, while on the other hand, they need... [to full text]