  The extension of the Boltzmann-Uehling-Uhlenbeck model of nucleus-nucleus
collision is presented. The isospin-dependent nucleon-nucleon cross sections
are estimated using the proper volume extracted from the equation of state of
the nuclear matter transformed into the form of the Van der Waals equation of
state. The results of such simulations demonstrate the dependence on symmetry
energy which typically varies strongly from the results obtained using only the
isospin-dependent mean-field. The evolution of the n/p multiplicity ratio with
angle and kinetic energy, in combination with the elliptic flow of neutrons and
protons, provides a suitable set of observables for determination of the
density dependence of the symmetry energy. The model thus provides an
environment for testing of equations of state, used for various applications in
nuclear physics and astrophysics.
