  We specify a tractable transport model with thermodynamic properties close to
those expected for the strongly interacting matter. In particular, at high
temperatures, the matter undergoes a phase transition, such as to the
quark-gluon plasma, with a drop in masses of elementary excitations and a rapid
increase in the number of degrees of freedom. We show that a softening of the
equation of state such as associated with the transition to quark-gluon plasma
should be observable in the elliptic-flow excitation function from heavy-ion
reactions.
