  Do fast vehicles always enjoy the benefits of being faster? The answer
depends on the dimension of the system. In one-dimensional systems, the whole
traffic dynamics depend strongly on the behaviour of the leading vehicle. Here,
we analyze general one-dimensional cellular-automata models of vehicular
traffic and show that if the models satisfy three properties -- the
interactions are unidirectional, the dynamics of the particles act as to
maximize the velocity and the particles are hard-particles -- them the average
velocity in the steady-state of any particle is not higher than the average
velocity of the slowest particle in the population. This very simple result
allows us to show a link between traffic theory and evolutionary graph theory
with the consequence that, if the driving styles spread through social
imitation, the driving style of the slowest driver dominates the population at
low particle densities. In terms of an evolutionary race, the slowest is the
winner just as in Aesop's fable the tortoise and the hare race.
