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1.
A. Namazi N. Eissfeldt P. Wagner A. Schadschneider 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):559-570
The Krauss-model is a stochastic model for traffic flow which is continuous in space. For periodic boundary conditions it
is well understood and known to display a non-unique flow-density relation (fundamental diagram) for certain densities. In
many applications, however, the behaviour under open boundary conditions plays a crucial role. In contrast to all models investigated
so far, the high flow states of the Krauss-model are not metastable, but also stable. Nevertheless we find that the current
in open systems obeys an extremal principle introduced for the case of simpler discrete models. The phase diagram of the open
system will be completely determined by the fundamental diagram of the periodic system through this principle. In order to
allow the investigation of the whole state space of the Krauss-model, appropriate strategies for the injection of cars into
the system are needed. Two methods solving this problem are discussed and the boundary-induced phase transitions for both
methods are studied. We also suggest a supplementary rule for the extremal principle to account for cases where not all the
possible bulk states are generated by the chosen boundary conditions.
Received 16 September 2002 / Received in final form 4 November 2002 Published online 31 December 2002 相似文献
2.
In this paper we study the congested patterns upstream of an isolated on-ramp in a cellular automaton traffic flow model, which is proposed in our previous paper [Cheng-Jie Jin, Wei Wang, Rui Jiang, Kun Gao, J. Stat. Mech (2010) P03018]. The simulation results under open boundary conditions are presented by spatiotemporal diagrams. Our diagram of congested patterns is quite similar to that of the cellular automaton models within Kerner’s three-phase traffic theory, while some differences in the “moving synchronized flow pattern” (MSP) should be noted. In our model the upstream front of MSP propagates not only upstream, but also downstream. The propagation direction depends on the flow rates and densities of free flow and synchronized flow. Besides, in our model the outflow of wide moving jams or bottlenecks could be free flow or synchronized flow, as reported in many empirical data. In the dissolving of congestions, the form of free flow may be hindered and stable synchronized flow may emerge. This phenomenon can help us understand more about the outflow. All the interesting characteristics of our model are due to the nonmonotonic structure of synchronized flow branch in the fundamental diagram, which has not been found in previous models. 相似文献
3.
We propose another possible mechanism of synchronized flow, i,e. that a time headway dependent randomization can exhibit synchronized flow. Based on this assumption, we present a new cellular automaton (CA) model for traffic flow, in which randomization effect is enhanced with the decrease of time headway. We study fundamental diagram and spatial-temporal diagrams of the model and perform microscopic analysis of time series data, which shows the model could reproduce synchronized flow as expected. It is also shown that a spontaneous transition from synchronized flow to jam could be observed by incorporating slow-to-start effect into the model. We expect that our work could contribute to the understanding of the real origin of synchronized flow. 相似文献
4.
The synchronized flow traffic phase of Kerner’s three-phase traffic theory can be well reproduced by the model proposed by Jiang and Wu [R. Jiang, Q.S. Wu, J. Phys. A: Math. Gen. 36 (2003) 381]. But in the Jiang and Wu model, the rule for brake light-after switching on, the brake light will not set off until the vehicle accelerates-is obviously unrealistic. Thus we improved the model by considering the difference in accelerating and decelerating performance under different driving conditions. The fundamental diagram and spatial-temporal diagrams are analyzed. We confirmed that the new model could reproduce the synchronized flow by two methods, i.e. the traffic flow interruption effect and performing microscopic analysis of time series data. Simulation results show that the decelerating difference is an important factor to reproduce the synchronized flow. We expect that our work could make contributions to understanding the mechanism of the synchronized flow. 相似文献
5.
6.
In this paper, we propose a new cellular automaton model based on the well known three-phase traffic theory. The model takes into account the mechanism of a driver’s oscillation behavior obtained from engineering experiments in real traffic conditions. This mechanism shows the inner competition between speed adaptation and distance adjustment effects. The speed adaptation effect leads to synchronized flow, whereas a pinch region emerges, associated with the spontaneous occurrence of wide moving jams, due to distance over-adjustment. Numerical simulations are carried out both with periodic and with open boundary conditions in order to investigate the spatiotemporal features of traffic flow. The results indicate that our model is able to reproduce the three distinct traffic phases and exhibit the four congested patterns upstream of an isolated on-ramp, which is in good consistency with the results predicted from the three-phase theory. 相似文献
7.
8.
We investigate two models for traffic flow with modified acceleration (‘slow-to-start’) rules. Even in the simplest case vmax = 1 these rules break the ‘particle-hole’ symmetry of the model. We determine the fundamental diagram (flow-density relationship) using the so-called car-oriented mean-field approach (COMF) which yields the exact solution of the basic model with vmax = 1. Here we find that this is no longer true for the models with modified acceleration rules, but the results are still in good agreement with simulations. We also compare the effects of the two different slow-to-start rules and discuss their relevance for real traffic. In addition, in one of these models we find a new phase transition to a completely jammed state. 相似文献
9.
R. Jiang M. B. Hu B. Jia R. L. Wang Q. S. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):267-273
This paper studies a new model, which considers the effects of
drivers reaction delay in the Nagel-Schreckenberg model. We studied
the traffic flow properties in the new model under both periodic and
open boundary conditions. The fundamental diagram, spatio-temporal
patterns, density-density correlation functions, relaxation time,
and distance headway distribution are investigated. Several
interesting results are reported, for example, (i) the jam becomes
less condensed when the delay effect is considered; (ii) the
distance headway of the new model exhibits a multi-peak distribution
when randomization p is small; (iii) for large p, the
distribution of distance headway follows a power law in the new
model; (iv) under open boundary conditions, the existence of a
stationary jam near the left boundary will lower the flow rate. 相似文献
10.
In this paper, we incorporate a limitation on the interaction range between neighboring vehicles into the cellular automaton model proposed by Gao and Jiang et al. [K. Gao, R. Jiang, S. X. Hu, B. H. Wang and Q. S. Wu, Phys. Rev. E 76 (2007) 026105], which was established within the framework of Kerner’s three-phase traffic theory and has been shown to be able to reproduce the three-phase traffic flow. This modification eliminates an unrealistic phenomenon found in the previous model, where the velocity-adaptation effect between neighboring vehicles can exist even if those vehicles are infinitely far away from each other. Therefore, in the improved model, we regulate that such interactions can only occur within a finite distance. For simplicity, we suppose a constant value to describe this distance in this paper. As a result, when compared to the previous model, the improved model mainly simulates the following results which are believed to be an improvement. (1) The improved model successfully reproduces the expected discontinuous transition from free flow to synchronized flow and the related “moving synchronized flow pattern”, which are both absent in the original model but have been observed in real traffic. (2) The improved model simulates the correlation functions, time headway distributions and optimal velocity functions which are all more consistent with the empirical data than the previous model and most of the other models published before. (3) Together with the previous two models considering the velocity-difference effect, this model finally accomplishes a significative process of developing traffic flow models from the traditional “fundamental diagram approach” to the three-phase traffic theory. This process should be helpful for us to understand the traffic dynamics and mechanics further and deeper. 相似文献
11.
The effect of stochastic accelerating and delay probability with the velocity and the gap between vehicles on traffic flow 下载免费PDF全文
This paper proposes a new combined cellular automaton (CA) model
considering the driver behavior of stochastic acceleration and delay
with the velocity of the preceding vehicle and the gap between the
successive vehicles based on the WWH model and the noise-first NaSch
model. It introduces the delay probability varying with the gap,
adds the anticipation headway and increases the acceleration with a
certain probability. Through these simulations, not only can the
metastable state and start--stop wave be obtained but also the synchronized flow
which the wide moving jam results in. Moreover, the
effect of stochastic acceleration and delay on traffic flow is
discussed by analyzing the correlation of traffic data. This indicates
that synchronized flow easily emerges in the critical area between
free flow and synchronized flow when acceleration and delay are
synchronized or their probability is close to 0.5. 相似文献
12.
This paper presents a cellular automaton model for single-lane traffic flow. On the basis of the Nagel-Schreckenberg (NS) model, it further considers the effect of headway-distance between two successive cars on the randomization of the latter one. In numerical simulations, this model shows the following characteristics. (1) With a simple structure, this model succeeds in reproducing the hysteresis effect, which is absent in the NS model. (2) Compared with the slow-tostart models, this model exhibits a local fundamental diagram which is more consistent to empirical observations. (3) This model has much higher efficiency in dissolving congestions compared with the so-called NS model with velocitydependent randomization (VDR model). (4) This model is more robust when facing traffic obstructions. It can resist much longer shock times and has much shorter relaxation times on the other hand. To summarize, compared with the existing models, this model is quite simple in structure, but has good characteristics. 相似文献
13.
In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic, the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters' size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speed- dependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.[第一段] 相似文献
14.
In this paper,we further analyze our cellular automaton(CA)traffic flow model.By changing some parameters,the characteristics of our model can be significantly varied,ranging from the features of phase transitions to the number of traffic phases.We also review the other CA models based on Kerner’s three-phase traffic theory.By comparisons,we find that the core concepts for modeling the synchronized flow in these models are similar.Our model can be a good candidate for modeling the synchronized flow,since there is enough flexibility in our framework. 相似文献
15.
This paper presents an improved cellular automata model, which is based on three phase traffic theory and
can reproduce the first
order phase transition from free flow to synchronized flow.
The fundamental diagram, the spacetime plots, and the 1-min average flux density diagram are presented.
The autocorrelation and cross correlation functions are studied to identity the synchronized flow state.
It is shown that the results of the model are well consistent with the empirical findings. 相似文献
16.
《Physica A》2002,303(1-2):251-260
Traffic flow at low densities (free traffic) is characterized by a quasi-one-dimensional relation between traffic flow and vehicle density, while no such fundamental diagram exists for ‘synchronized’ congested traffic flow. Instead, a two-dimensional area of widely scattered flow-density data is observed as a consequence of a complex traffic dynamics. For an explanation of this phenomenon and transitions between the different traffic phases, we propose a new class of molecular-dynamics like microscopic traffic models based on times to collisions and discuss the properties by means of analytical arguments. Similar models may help to understand the laminar and turbulent phases in the dynamics of stock markets as well as the transitions among them. 相似文献
17.
The traditional cellular automaton (CA) model assumes that drivers only receive information from the preceding vehicles, e.g. the brake light information. However, in reality, drivers not only perceive information from downstream but can also get upstream information, e.g. the honk stimulation. The CA model involving traffic information from downstream and upstream is called the bi-directional CA model here. Meanwhile, with the introduction of Connected Vehicle Technologies, the perception range of drivers is expected to significantly increase which can lead to more informed driving behavior. Such an impact cannot be easily modeled by traditional one-directional CA models. In this study, the perception ranges of both the brake light effect and honk stimulation are introduced into the bi-directional CA model. Fundamental diagrams and spatial–temporal diagrams are then analyzed and two methods, i.e. the traffic flow interruption effect and microscopic analysis of time series data, are utilized to distinguish the synchronized traffic flow. Further numerical results illustrate that the perception range and slow-to-start sensitivity threshold are two important factors to reproduce the synchronized flow, and consideration of the honk information and the larger perception range both benefit the stability of traffic flow, which implies the potential significance of the application of Connected Vehicle Technologies. 相似文献
18.
Analytical investigation of the boundary-triggered phase transition dynamics in a cellular automata model with a slow-to-start rule 下载免费PDF全文
Previous studies suggest that there are three different jam phases in the cellular automata automaton model with a slow-to-start rule under open boundaries.In the present paper,the dynamics of each free-flow-jam phase transition is studied.By analysing the microscopic behaviour of the traffic flow,we obtain analytical results on the phase transition dynamics.Our results can describe the detailed time evolution of the system during phase transition,while they provide good approximation for the numerical simulation data.These findings can perfectly explain the microscopic mechanism and details of the boundary-triggered phase transition dynamics. 相似文献
19.
Francisco C. Alcaraz Clisthenis P. Constantinidis 《Journal of statistical physics》1990,60(5-6):639-657
We introduce and study the critical properties of the tripletXY quantum chain. This system is described in terms of three-spin interactions and is the generalization of the standardXY quantum chain. We show that this model, with periodic boundaries, has a local gauge invariance and can be described by the composition of two triplet Ising models, with general toroidal boundary conditions. From this composition the phase diagram as well the conformai anomaly and critical exponents are determined by exploring their relations with the mass gap amplitudes predicted by conformai invariance. 相似文献
20.
用解析分析与数值仿真的手段研究了一种典型的车辆跟驰模型(OV模型)与元胞自动机模型(NS模型)之间的区别与联系.首先通过对模型规则的分析,证明了确定NS模型是OV模型的一种离散形式.随后针对两模型更复杂的具体形式,通过数值仿真的手段进行了模型的密度-流量关系与模型在开放边界下的动态特性的研究.实验结果表明,从现象来看,OV模型与NS模型具有非常近似的性质,但两种模型的机制不相同,并且各自具有不能相互替代的优势.为交通流模型的使用和改进提供了参考. 相似文献