  A model equation has been proposed to describe bimodal features in vehicular
traffic flows. The dynamics of the bimodal distribution reveals the existence
of a fixed point that is connected to itself by a homoclinic trajectory. The
mathematical conditions associated with bimodality have been established. The
critical factors necessary for both a breaking of symmetry and a transition
from bimodal to unimodal behaviour, in the manner of a bifurcation, have been
analysed.
