  We study the formation, evolution and structure of dissipative fronts
produced by overtaking collisions of relativistic streams, with emphasis on
strongly magnetized flows. The evolution of the system is followed using
analytical approach in the simple wave regime and numerical simulations in the
non-simple wave regime, until a steady-state is reached. The steady-state
structure of the front is then examined by solving the appropriate jump
conditions. The conversion of magnetic energy into kinetic energy is
parametrized in terms of the Alfv\'en 4-velocity inside the front. The
implications for gamma-ray jets are briefly discussed.
