  The gas-kinetic foundation of fluid-dynamic traffic equations suggested in
previous papers [Physica A 219, 375 and 391 (1995)] is further refined by
applying the theory of dense gases and granular materials to the Boltzmann-like
traffic model by Paveri-Fontana. It is shown that, despite the
phenomenologically similar behavior of ordinary and granular fluids, the
relations for these cannot directly be transferred to vehicular traffic. The
dissipative and anisotropic interactions of vehicles as well as their
velocity-dependent space requirements lead to a considerably different
structure of the macroscopic traffic equations, also in comparison with the
previously suggested traffic flow models. As a consequence, the instability
mechanisms of emergent density waves are different. Crucial assumptions are
validated by empirical traffic data and essential results are illustrated by
figures.
