Before revision:  Collisions in a non-equilibrium system with mass conservation, a common property of natural systems, exhibit rich dynamics that range from soliton-like to annihilation, and even nucleation of new pulses post-collision. Mass-conservation is shown to be a key ingredient for this behavior to occur robustly over a wide range of parameters.
After revision:  Collisions in a non-equilibrium system with mass conservation, a common property of natural systems, exhibit rich dynamics that range from soliton-like crossover and pulse nucleation if the system obeys a mass conservation constraint. In contrast to previous observations in systems without mass conservation, these alternative collision scenarios are robustly observed over a wide range of parameters.