  A relativistic 3-fluid 3D hydrodynamic model has been developed for
describing heavy-ion collisions at incident energies between few and $\sim$ 200
A$\cdot$GeV. In addition to two baryon-rich fluids which simulate mutually
decelerating counterflows of target and projectile nucleons, the new model
incorporates evolution of a third, retarded baryon-free fluid created by this
decelerated baryonic matter. Different equations of state, including those with
the deconfinement phase transition, are treated. A reasonable agreement with
experiment is illustrated by proton rapidity spectra, their dependence on
collision centrality and beam energy.
