A review of an empirical study of traffic phases and phase transitions in traffic flow is presented. A critical comparison of model results and results of traffic theories with of real features of traffic phase is given. A qualitative theory of congested traffic flow recently developed is discussed. Up to now it was almost self-evident that both homogeneous and time independent solutions of a mathematical traffic flow model should belong to a curve on the flow-density plane which goes through the original and has at least one maximum. This curve is called the fundamental diagram for traffic flow. It represents the obvious result of experimental observations that the higher the vehicle density in traffic flow, the lower the average vehicle speed. Recall that real traffic can be in either free or in congested regime. Empirical points corresponding to free flow can be represented by a curve on the flow density plan which is cut off at some limit point. Congested traffic can be determined as states of traffic where the average vehicle speed is lower than the minimum possible speed which is related to this limit point. It is well-known that within congestion, the flow-density data do not form a neat relationship but show a broad and complex spreading of measurement points, that is, the flow-density data cover a two-dimensional region on the flow-density plane. This complexity in traffic flow is usually interpreted either as fluctuations, or as an instability, or else as a traffic jam formation. These features of real traffic flow should be explained by traffic models. The physics of traffic flow is proving to be much richer than most mathematicians and physicists working in the field had expected. Recent experimental observations of real traffic patterns have discovered new phases of traffic flow, such as synchronized flow, and revealed a large number of features that are qualitatively similar to those observed in other non-linear systems. The next challenge in this field is to develop new mathematical and theoretical concepts to explain these features.


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    Title :

    Discovering of synchronized flow as a new traffic phase and related problems for traffic flow modeling


    Contributors:


    Publication date :

    2002


    Size :

    7 Seiten, 4 Bilder, 9 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English





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