In this paper, we address the problem of controlling traffic lights at an intersection with a wireless sensor network. We propose a wireless sensor network architecture that does not depend on a centralized coordinator and we separate logically this distributed network into 4 levels of hierarchy. On this architecture, we define and evaluate through simulation a phases selection algorithm that decides dynamically of the movements composing the next phase and of the duration of this phase. Simulation results show that this algorithm, if properly tuned, has the capacity to reduce average waiting time at an intersection, while avoiding starvation for multiple load levels.