Abstract
We study the dynamics of a lattice gas with two species of "charged" diffusing particles in the presence of an external field. There are several time scales characterizing the approach of the steady state. At short times diffusion smears out inhomogeneities. For fields such that the density is below the virtual (size-dependent) threshold of jamming, i.e. in the flow phase, this is the main relaxation mechanism. In addition, there are kinematic waves arising from the non-linear dependence of the current on the density. Above the threshold there is an instability leading to a multistrip structure of blockages: in each strip one type of particle prevents the other type from following the direction of the imposed field. The strips coarsen logarithmically slowly, until finally a single blockage remains.