  The dynamics of cosmological anisotropies is investigated for Bianchi type I
universe filled by a relativistic matter represented by the reduced
relativistic gas model (RRG), with equation of state interpolating between
radiation and matter. Previously it was shown that the interpolation is
observed in the background cosmological solutions for homogeneous and isotropic
universe and also for the linear cosmological perturbations. We extend the
application of RRG to the Bianchi type I anisotropic model and find that the
solutions evolve to the isotropic universe with the pressureless matter
contents.
