Abstract
A microscopic model for phase transitions in traffic flow is presented. The basic assumption of the model is that hypothetical homogeneous and stationary, i.e. `equilibrium' states of the model cover a two-dimensional region in the flow-density plane. As in empirical observations, in the model moving jams do not spontaneously occur in free flow. Instead, the first-order phase transition to synchronized flow beginning at some density in free flow is realized. The moving jams emerge only in synchronized flow. As a result, the diagrams of patterns (states) both for a homogeneous road without bottlenecks and at on-ramps are qualitatively different from those found in other approaches at present. In particular, only one type of pattern occurs at on-ramps, if the flow rates to the on-ramp and on the road are high enough: in this general pattern synchronized flow occurs upstream of the on-ramp and wide moving jams spontaneously emerge in this synchronized flow.