  In one-dimensional, heterogeneous systems, the whole traffic dynamics depend
strongly on the behavior of the leading vehicle. This result holds for a class
of vehicular traffic models satisfying the following properties. The
interactions are unidirectional. The dynamics of the particles maximize the
velocity or reduces the gap between particles. The particles are hard. We use
this result to show a link between traffic models and graphs theory with the
consequence that as driving styles spread through social contagion and appear
randomly, the inhomogeneities of the system becomes dynamical, or
\textit{annealed}, toward specific regions in the space of parameters.
Interpreting parameters as entries of vectors defined in the parameters space
appear analogies between the evolutionary dynamics of these systems and
asymptotic behaviors of the \textit {n-vector model}. When the time-scale ratio
of imitation to the mutation processes, $ \tau_i / \tau_m $, is small an
organized state where "orientation" corresponds to the set of parameters of the
slowest strategies is favored, and if this ratio is big an unorganized state
without a preferential orientation is favored.
