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The effect of a bottleneck (a gate) and a delayed-start signal, which controls the start of every car, on the flow of cars in a one-dimensional highway is studied on the basis of Fukui–Ishibashi model, where the maximum speed assigned to each car is set to M. The car density pj in the jam flow region formed before the gate is found to play a key role in determining the constant flow FC. We have derived the formulas for pj in terms of the probability f of the delayed-start and the probability r of the gate being open, which does not contradict with some special cases, such as the gate always opens (r = 1) or no car receives the delayed-start signal (f = 0). To test the validity of the obtained formulas, detailed computer simulations were performed. It was found that the formulas reproduce the cellular automaton simulation results fairly well in the entire range of f and r despite the simplicity of the mathematical derivation. The targeted diagram of the constant flow FC obtained in the intermediate density range as a function of M, f, and r is completed. [ABSTRACT FROM AUTHOR]

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]

We show detailed data about the process of jam formation in a traffic experiment on a circuit without any bottlenecks. The experiment was carried out using a circular road on a flat ground. At the initial stage, vehicles are running homogeneously distributed on the circuit with the same velocity, but roughly 10 min later a traffic jam emerges spontaneously on the circuit. In the process of the jam formation, we found a homogeneous flow with large velocity is temporarily realized before a jam cluster appears. The instability of such a homogeneous flow is the key to understanding jam formation. [ABSTRACT FROM AUTHOR]

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]