Can we determine the nuclear equation of state from heavy ion collisions?

We discuss the problems involved in extracting the nuclear equation-of-state from heavy-ion collisions. We demonstrate that the equation of state becomes effectively softer in non-equilibrium and this effect is observable in terms of collective flow effects. Thus, non-equilibrium effects must be included in transport descriptions on the level of the effective mean fields. A comparison with transverse momentum, rapidity, and centrality selected flow data show the reliability and limitations of the underlying interaction which was derived from microscopic Dirac-Brueckner (DB) results.