  In this work we study the effect of a traffic light system on the flow of a
single lane road by proposing a traffic model based on a cellular automaton
that also includes behavioral considerations. We focus on the macroscopic
characterization of the system by studying the changes in vehicle density and
the occurrence of jams. In this context we observe and characterize a phase
transition between the free flow and jammed states. This transition is induced
by the instabilities originated by the vehicles stopping at the traffic lights.
Moreover, we analyze the effect of these instabilities on the critical density
of vehicles at which the transition occurs as a function of two parameters: (i)
the in-flow of cars, (ii) the drivers' behavior. For the latter we observe that
the traffic light perturbations feedback on the drivers behavior can lead the
system to different scenarios, which are also analyzed.
