  Transport coefficients are of crucial importance in theoretical as well as
experimental studies. Despite substantial research on classical hard
sphere/disk gases in low and high density regimes, a thorough investigation of
transport coefficients for massive relativistic systems is missing in the
literature. In this work a fully relativistic molecular dynamics simulation is
employed to numerically obtain the transport coefficients of a hard sphere
relativistic gas based on Helfand-Einstein expressions. The numerical data are
then used to check the accuracy of Chapmann-Enskog (CE) predictions in a wide
range of temperature. The results indicate that while simulation data in low
temperature regime agrees very well with theoretical predictions, it begins to
show deviations as temperature rises, except for the thermal conductivity which
fits very well to CE theory in the whole range of temperature. Since our
simulations are done in low density regimes, where CE approximation is expected
to be valid, the observed deviations can be attributed to the inaccuracy of
linear CE theory in extremely relativistic cases.
