PHASE-TRANSITIONS IN 2-DIMENSIONAL TRAFFIC-FLOW MODELS

We introduce two simple two-dimensional lattice models to study traffic dow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phrase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite-size limit.