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Abstract: The jamming transition in a two-dimensional traffic network is investigated based upon the cellular automaton simulations, where the update rule is deterministic, though the initial car configuration is randomly set. The lifetime of the system is defined as the time until when all cars in the system come to a stop, and it will increase with decreasing car density from a higher density side. The critical car density is defined as the car density, at which the corresponding lifetime diverges. The analytical expression for the critical car density is proposed. [Copyright &y& Elsevier]

The emergence of a traffic jam is considered to be a dynamical phase transition in a physics point of view; traffic flow becomes unstable and changes phase into a traffic jam when the car density exceeds a critical value. In order to verify this view, we have been performing a series of circuit experiments. In our previous work (2008 New J. Phys.10 033001), we demonstrated that a traffic jam emerges even in the absence of bottlenecks at a certain high density. In this study, we performed a larger indoor circuit experiment in the Nagoya Dome in which the positions of cars were observed using a high-resolution laser scanner. Over a series of sessions at various values of density, we found that jammed flow occurred at high densities, whereas free flow was conserved at low densities. We also found indications of metastability at an intermediate density. The critical density is estimated by analyzing the fluctuations in speed and the density–flow relation. The value of this critical density is consistent with that observed on real expressways. This experiment provides strong support for physical interpretations of the emergence of traffic jams as a dynamical phase transition. [ABSTRACT FROM AUTHOR]

Abstract: A new two-dimensional cellular automaton traffic model is proposed, where blocks are placed periodically. The present model includes the model of two crossing roads in the limit of maximum sized blocks and the BML model in the limit of zero sized blocks. New phases of traffic flow appear between the free flow phase and the jam phase in the BML model. The boundaries between these phases come closer as the size of the block decreases and converge into one phase boundary at a density around 0.19, which is in fair agreement with the critical density in the BML model. [Copyright &y& Elsevier]

A traffic jam on a highway is a very familiar phenomenon. From the physical viewpoint, the system of vehicular flow is a non-equilibrium system of interacting particles (vehicles). The collective effect of the many-particle system induces the instability of a free flow state caused by the enhancement of fluctuations, and the transition to a jamming state occurs spontaneously if the average vehicle density exceeds a certain critical value. Thus, a bottleneck is only a trigger and not the essential origin of a traffic jam. In this paper, we present the first experimental evidence that the emergence of a traffic jam is a collective phenomenon like 'dynamical' phase transitions and pattern formation in a non-equilibrium system. We have performed an experiment on a circuit to show the emergence of a jam with no bottleneck. In the initial condition, all the vehicles are moving, homogeneously distributed on the circular road, with the same velocity. The average density of the vehicles is prepared for the onset of the instability. Even a tiny fluctuation grows larger and then the homogeneous movement cannot be maintained. Finally, a jam cluster appears and propagates backward like a solitary wave with the same speed as that of a jam cluster on a highway. [ABSTRACT FROM AUTHOR]