  We give a reminder on the major inputs of microscopic hadronic transport
models and on the physics aims when describing various aspects of relativistic
heavy ion collisions at SPS energies. We then first stress that the situation
of particle ratios being reproduced by a statistical description does not
necessarily mean a clear hint for the existence of a fully isotropic momentum
distribution at hadrochemical freeze-out. Second, a short discussion on the
status of strangeness production is given. Third we demonstrate the importance
of a new collective mechanism for producing (strange) antibaryons within a
hadronic description, which guarantees sufficiently fast chemical
equilibration.
