The investigations consider a driven lattice gas of interacting particles with open boundaries within a mean field treatment. We confirm the result obtained by J. Krug that the external conditions induce a phase transition. In the case of a square lattice with repulsive interactions, the phase transition is an order-disorder one which leads to the coexistence of ordered and disordered domains. The dynamical phase transition consists in the break down of the lattice occupation symmetry then in a rapid relaxation of the order parameter. The latter regime is characterised by the growth of the available space for the superstructure tilt the saturation of the maximal value of the order parameter. The onset of this steady state leads to the dynamical phase diagram to approach the statistical one except around critical points. A preliminary study of the interface delimiting the ordered and disordered regions is also given. We show that the transition influences the localisation of the interface called: “the diffusion front “.