  The hadronic phase in ultrarelativistic nuclear collisions has a large
influence on final state observables like multiplicity, flow and $p_t$ spectra,
as studied in the UrQMD approach. In this model one assumes that a
non-equilibrium decoupling phase follows a fluid dynamical description of the
high density phase. Hadrons are produced assuming local thermal equilibrium and
dynamically decouple during the hadronic rescattering until the particles are
registered in the detectors. This rescattering of hadrons modifies every
hadronic bulk observable. The apparent multiplicity of resonances is suppressed
as compared to a chemical equilibrium freeze-out model, because the decay
products rescatter. Therefore the resonances, which decay in the early hadronic
phase, cannot be identified anymore by the invariant mass method. Stable and
unstable particles change their momentum distribution by more than 30$\%$
through rescattering and their multiplicity is modified by resonance production
and annihilation on a similar magnitude. These findings show that it is all but
trivial to conclude from the final state observables on the properties of the
system at an earlier time where it may have been in local equilibrium.
