  Starting from interaction rules based on two levels of stochasticity we study
the influence of the microscopic dynamics on the macroscopic properties of
vehicular flow. In particular, we study the qualitative structure of the
resulting flux-density and speed-density diagrams for different choices of the
desired speeds. We are able to recover multivalued diagrams as a result of the
existence of a one-parameter family of stationary distributions, whose
expression is analytically found by means of a Fokker-Planck approximation of
the initial Boltzmann-type model.
