  In a recent publication [Phys. Rev. E \textbf{83}, 011301 (2011)],
Vollmayr--Lee \emph{et al.} have determined by computer simulations the thermal
diffusivity and the longitudinal viscosity coefficients of a driven granular
fluid of hard spheres at intermediate volume fractions. Although they compare
their simulation results with the predictions of kinetic theory, they use the
dilute expressions for the driven system and the modified Sonine approximations
for the undriven system. The goal here is to carry out this comparison by
proposing a modified Sonine approximation to the Enskog equation for driven
granular fluids that leads to a better quantitative agreement.
