  Transverse mass spectra of pions and protons measured in central collisions
of heavy ions at the SPS and at RHIC are compared to a hydrodynamic
parameterization. While the chemical temperature needed at RHIC is
significantly higher compared to SPS, the spectra may be described using
kinetic freeze-out parameters which are similar for both beam energies. At RHIC
either the temperature or the flow velocity is higher, but the data provide no
unambiguous proof for much stronger transverse flow. The contribution of such
hydrodynamic emission at high transverse momenta is investigated in detail. It
is shown that hydrodynamics may be relevant up to relatively high transverse
momenta. The importance of the velocity profile used in this context is
highlighted.
