  We use a macroscopic description of a system of relativistic particles based
on adding a nonequilibrium tensor to the usual hydrodynamic variables. The
nonequilibrium tensor is linked to relativistic kinetic theory through a
nonlinear closure suggested by the Entropy Production Principle; the evolution
equation is obtained by the method of moments, and together with
energy-momentum conservation closes the system. Transport coefficients are
chosen to reproduce second order fluid dynamics if gradients are small. We
compare the resulting formalism to exact solutions of Boltzmann's equation in
0+1 dimensions and show that it tracks kinetic theory better than second order
fluid dynamics.
