Recently, as performance of computers improves, it is possible to simulate larger-scale and more detailed traffic flows. In this paper, a road traffic system is modeled as a hierarchical autonomous decentralized system by constructing three kinds of the model which correspond to roads, vehicles and drivers respectively. By modeling the vehicles and drivers separately, it is possible to consider independently a physical dynamics of the system and issues related to information and decision makings. By comparing the results of simulation using the proposed model with those obtained by the Underwood model, the validity of the proposed model has been confirmed. Moreover, the typical phenomenon in actual traffic flows in sag has been also observed in the simulation. Finally, as an example of the utilization of the simulation model, the effects of the introduction of speed limit on traffic flows have been examined.
