  From the requirement of continuous matching of bulk metric around the point
of brane collision we derive a conservation law for collisions of p-branes in
(p+2)-dimensional space-time. This conservation law relates energy densities on
the branes before and after the collision. Using this conservation law we are
able to calculate the amount of matter produced in the collision of
orbifold-fixed brane with a bulk brane in the ``ekpyrotic/pyrotechnic type''
models of brane cosmologies.
