  We develop a combined hydro-kinetic approach which incorporates a
hydrodynamical expansion of the systems formed in \textit{A}+\textit{A}
collisions and their dynamical decoupling described by escape probabilities.
The method corresponds to a generalized relaxation time ($\tau_{\text{rel}}$)
approximation for the Boltzmann equation applied to inhomogeneous expanding
systems; at small $\tau_{\text{rel}}$ it also allows one to catch the viscous
effects in hadronic component - hadron-resonance gas. We demonstrate how the
approximation of sudden freeze-out can be obtained within this dynamical
picture of continuous emission and find that hypersurfaces, corresponding to a
sharp freeze-out limit, are momentum dependent. The pion $m_{T}$ spectra are
computed in the developed hydro-kinetic model, and compared with those obtained
from ideal hydrodynamics with the Cooper-Frye isothermal prescription. Our
results indicate that there does not exist a universal freeze-out temperature
for pions with different momenta, and support an earlier decoupling of higher
$p_{T}$ particles. By performing numerical simulations for various initial
conditions and equations of state we identify several characteristic features
of the bulk QCD matter evolution preferred in view of the current analysis of
heavy ion collisions at RHIC energies.
