  A simple model with a novel type of dynamics is introduced in order to
investigate the emergence of self-ordered motion in systems of particles with
biologically motivated interaction. In our model particles are driven with a
constant absolute velocity and at each time step assume the average direction
of motion of the particles in their neighborhood with some random perturbation
($\eta$) added. We present numerical evidence that this model results in a
kinetic phase transition from no transport (zero average velocity, $| {\bf v}_a
| =0$) to finite net transport through spontaneous symmetry breaking of the
rotational symmetry. The transition is continuous since $| {\bf v}_a |$ is
found to scale as $(\eta_c-\eta)^\beta$ with $\beta\simeq 0.45$.
