Synchronized Traffic Flow and Metastable States from the Perspective of Constant Time Headway

In the past decade, perhaps one of the most important findings in traffic flow field is the "synchronized flow\´\´. In previous literature, various mechanisms have been presented to explain synchronized flow. This paper proposes that trying to keep a constant time headway might be another possible origin of synchronized flow. The simulation of this effect is performed based on a cellular automaton model. The fundamental diagram and the spatiotemporal patterns are studied. It is shown that our model could reproduce metastable states of congested flow. We argue that in the metastable states, the traffic flow is alternation of free flow and synchronized flow. The velocity of the synchronized flow changes when traffic flow transits from one metastable state to another metastable state. Moreover, the synchronized flow could also spontaneously transit into jams. Within the jams, there exist blanks, which is consistent with the empirical observations.