  We analyze the large-scale dynamics of vortex lattices and charge density
waves driven in a disordered potential. Using a perturbative coarse-graining
procedure we present an explicit derivation of non-equilibrium terms in the
renormalized equation of motion, in particular Kardar-Parisi-Zhang
non-linearities and dynamic strain terms. We demonstrate the absence of glassy
features like diverging linear friction coefficients and transverse critical
currents in the drifting state. We discuss the structure of the dynamical phase
diagram containing different elastic phases very small and very large drive and
plastic phases at intermediate velocity.
