  Using simulations we examine a two-dimensional disk system in which two disk
species are driven in opposite directions. We measure the average velocity of
one of the species versus the applied driving force and identify four phases as
function of drive and disk density: a jammed state, a completely phase
separated state, a continuously mixing phase, and a laning phase. The
transitions between these phases are correlated with jumps in the
velocity-force curves that are similar to the behavior observed at dynamical
phase transitions in driven particle systems with quenched disorder such as
vortices in type-II superconductors. In some cases the transitions between
phases are associated with negative differential mobility in which the average
absolute velocity of either species decreases with increasing drive. We also
consider the situation where the drive is applied to only one species as well
as systems in which both species are driven in the same direction with
different drive amplitudes. Finally, we discuss how the transitions we observe
could be related to absorbing phase transitions where a system in a phase
separated or laning regime organizes to a state in which contacts between the
disks no longer occur and dynamical fluctuations are lost.
