  Generalizing previous work, we study the collision of massless superstring
plane waves in D space-time dimensions within an explicitly
O(D-2,D-2)-invariant set of field equations. We discuss some general properties
of the solutions, showing in particular that they always lead to the formation
of a singularity in the future. Using the above symmetry, we obtain entire
classes of new analytic solutions with non-trivial metric, dilaton and
antisymmetric field, and discuss some of their properties of specific relevance
to string cosmology.
