一种改进Nagel-Schreckenberg模型在开放边界条件下交通流的研究

研究了一种改进的Nagel-Schreckenberg模型在开放边界条件下交通流的性质，分析了边界条件，安全距离，刹车概率对交通流的影响. 关键词： 元胞自动机 交通流 安全距离 延迟起动     

开放性边界条件下双车道元胞自动机交通流模型耦合效应研究

在一种改进的Nagel-Schrekenberg元胞自动机交通流模型的基础上，提出一个高速公路双车 道元胞自动机模型来模拟开放性边界条件下的车流运动，并考虑两车道之间左边界开放程度 的比例系数α及车辆加减速概率p的影响.计算机数值模拟结果表明，在车流状态的演化过程 中，通过确定车道耦合系数b来控制车流量，不同的b值车流量不同，对车辆运动出现堵塞项 的相变点有影响. 关键词： 元胞自动机 交通流模型 耦合效应     

开放边界条件下平面环行交叉路口交通流的相图研究

运用具有内、外环车道的平面环形交叉路口元胞自动机模型,对开放边界条件下平面环行交叉路口的交通流进行研究.计算机模拟结果表明:边界条件和道路瓶颈影响着平面环形交叉路口交通流的性质,产生概率和消失概率均只在一定范围内影响系统流量的变化.根据系统流量与产生概率和消失概率的关系,将系统分为三个相区,并对相图进行研究,为实际交通控制提供参考.     

开放边界条件下二维可转向主干道交通流模型的研究

在开放性边界条件下，利用改进的Nagel-Schreckenberg交通流模型，引入过路口车辆的可 转向机理，建立二维n速主干道元胞自动机交通流模型，研究了转向概率和边界条件对 干道交通状况的影响而导致的不同相变特性以及这两个因素对实现改善干道交通的组织作用 . 关键词： 元胞自动机 交通流 转向概率 相变     

智能交通灯对交叉路口交通流的影响

以改进的NaSch模型为基础,采用开放边界条件,分别对普通交通灯和智能交通灯控制下的十字交叉路口交通流进行模拟.结果表明,主干道车辆较多时,智能交通灯控制下的主干道车辆平均速度和流量都比普通交通灯控制下高,并可减少车辆的无谓等待时间. 关键词： 元胞自动机 交叉路口 智能交通灯 NaSch模型     

速度限制对交通流的影响

运用元胞自动机模型研究单车道路面上设立限速区对交通流的影响.计算机模拟结果显示,在交通流与密度的基本图中存在饱和交通流量,其大小取决于限速区的最大速度.限速区的设立导致不同相的分离.在确定性的模型中,当车辆密度较低时,存在两种不同的自由流相;而当车辆密度较高时,出现最大交通流相和自由流相.在随机模型中,车辆密度较高时,出现最大交通流相-堵塞相-自由流.对交通流以及临界密度等量给出一些解析结果.     

混合状态下城市快速路交通流短时预测

建立交通流短时预测状态空间模型, 研究混合状态下城市快速路交通流短时预测. 结合城市快速路自由流状态、拥挤流状态和阻塞流状态下交通流参数的时间和空间分布特性, 基于交通流守恒方程和速度动态模型, 借鉴偏微分方程组求解时空离散的思想, 建立三种状态下交通流短时预测模型; 同时考虑进出口匝道、车道数变更以及道路坡度等因素的影响, 将交通流短时预测模型转化为交通流短时预测状态空间模型, 实现混合状态下交通流短时预测. 研究表明, 该方法能够实现混合状态下道路网内的交通流短时预测, 预测精度可达90.23%. 相同条件下, 经典自回归滑动平均模型的预测精度仅为81%. 关键词： 交通流短时预测 自由流状态 拥挤流状态 阻塞流状态     

匝道系统减速车道对高速公路交通流的影响

主要研究匝道系统减速车道对高速公路交通流的影响.在开放边界条件下,以NaSch模型为基础,建立了含减速车道的出口匝道系统双车道元胞自动机交通流模型.通过计算机数值模拟,得出不同参数控制下的密度、速度、流量和车辆产生概率关系图像,并与不设减速车道的匝道系统进行比较. 关键词： 元胞自动机 匝道 减速车道 NaSch模型     

双流体颗粒-壁面碰撞模型用于旋流流动

对旋流两相流动,用考虑壁面粗糙度的双流体颗粒-壁面碰撞模型,结合二阶矩两相湍流模型和不同颗粒相边界条件,进行了数值模拟。结果表明,由于考虑了各方向雷诺应力之间的相互转化,雷诺应力从平均运动中得到能量,以及壁面对颗粒运动的衰减作用等因素,该颗粒壁面碰撞模型给出的模拟结果与实验符合较好,而广泛应用的零梯度颗粒壁面边界条件给出的模拟结果最差。     

一种改进的一维元胞自动机交通流模型及减速概率的影响

在Nagel-Schrekenberg单车道元胞自动机交通流模型的基础上,考虑车辆之间的相对运动以及车辆减速概率对交通状态的影响,提出了一种改进的单车道元胞自动机交通流模型.并以该模型进行计算机模拟,结果表明,在车流状态的演化过程中,通过确定减速概率与车辆密度的指数v关系来控制车流量,不同的v值车流量不同,对车辆运动出现堵塞相的相变点有影响.当v约为0.75时,模拟结果与实测结果符合.随着车辆密度的增加,车辆的局域聚集程度加大,平均速度下降增大,将出现不稳定的车辆聚集的堵塞相.在车辆的运动过程中,车流的运 关键词： 交通流 元胞自动机 减速概率 堵塞相     

考虑行车状态的一维元胞自动机交通流模型

在Nagel Schrekenberg单车道元胞自动机交通流模型（简称NS模型）的基础上，考虑车辆之间的相对运动薛郁等提出了一种改进的单车道元胞自动机交通流模型（简称改进的NS模型）.通过两种情况列出了改进的NS模型存在不尽周严的地方，随之在新模型中引入了行车状态 变量和反馈规则，从而控制车辆出现倒车和刹车过急等现象.通过计算机对新模型进行模拟 ，发现减速概率和车流密度对车流状态的演化影响很大，当减速概率高（如道路条件差）时 ，即使车流密度低，车流也会出现局部堵塞状态；而当减速概率一定时，随着车流密度增加 ，车流的运动相与堵塞相发生了全局性的交替出现，此时类似于波的波峰和波谷的传播.与 改进的NS模型相比较，新模型模拟的车流量较高，说明新模型减少了车流的总体停滞状态. 关键词： 交通流 元胞自动机 行车状态 反馈规则     

An improved cellular automaton traffic model considering gap-dependent delay probability

In this paper, the delay probability of the original Nagel and Schreckenberg model is modified to simulate one-lane traffic flow. The delay probability of a vehicle depends on its corresponding gap. According to simulation results, it has been found that the structure of the fundamental diagram of the new model is sensitively dependent on the values of the delay probability. In comparison with the NS model, one notes that the fundamental diagram of the new model is more consistent with the results measured in the real traffic, and the velocity distributions of the new model are relatively reasonable.     

An improved cellular automaton model with the consideration of a multi-point tollbooth

Based on the classical Nagel–Schreckenberg model, we in this paper propose an improved cellular automaton (CA) model to study the influences of a multi-point tollbooth on traffic flow. The numerical results show that the multi-point tollbooth can be looked at as a bottleneck and that it can improve the road capacity compared with other tolling stations, which shows that the proposed model is more effective than other traffic flow models. In addition, the results can help readers to better understand the effects of a multi-point tollbooth on traffic flow and help traffic engineers to reasonably design the tolling station.     

Analytic approach to the critical density in cellular automata for traffic flow

The jamming transition in the stochastic traffic cellular automaton of Nagel and Schreckenberg [J. Phys. I 2, 2221 (1992)] is examined. We argue that most features of the transition found in the deterministic limit do not persist in the presence of noise, and suggest instead to define the transition to take place at that critical density rho(c) at which a large initial jam just fails to dissolve. We show that rho(c)=v(J)/(v(J)+v(F)), where v(F) is the velocity of noninteracting vehicles and v(J) is the speed of the dissolution wave moving into the jam. An approximate analytic calculation of v(J) in the framework of a simple renormalization scheme is presented, which explicitly displays the effect of the interaction between vehicles during the acceleration stage of the Nagel-Schreckenberg rules with maximum velocity v(max)>1. The analytic prediction is compared to numerical simulations. We find a remarkable correspondence between the analytic expression for v(J) and a phase diagram obtained numerically by Lübeck et al.     

元胞自动机交通流模型的相变特性研究

系统地研究 VDR模型和T²模型在不同车流密度时车辆位置的相关性. 通过VDR模型、BJH模型和T²模型的序参量计算，确定在这三个模型中车流从自由流动到阻塞的相变特性，结果发现引入慢启动规则后，在不同的延迟概率和最大速度情况下，将引起交通相变特性的改变. 关键词： 交通流 元胞自动机 相关函数 序参量     

Effect of the lane reduction in the cellular automata models applied to the two-lane traffic

More investigated situations in the field of traffic modelling are those of traffic bottlenecks caused by slow vehicles or road defects. The new aspect of this paper is the simulation of vehicular dynamics near a partial reduction in a road from two lanes to one lane. In order to reduce the bad impact of waiting vehicles behind the defect region, a strategy regulating the vehicle movement in the vicinity of the reduced lane is taken into account. The simulation model is based on the cellular automata model of Nagel–Schreckenberg with additional rules of lane change. The partial lane reduction strongly reduces the road capacity, and the added regulation strategy leads to a more interesting shape of the fundamental diagram, which depends on different constraints on the model parameters, e.g., the length of the reduced lane, the maximal speed, and the length of the connection sites near the entry of the reduced lane.     

First order phase transition from free flow to synchronized flow in a cellular automata model

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.     

Cellular automaton model within the fundamental-diagram approach reproducing some findings of the three-phase theory

We propose a simple cellular automaton for traffic flow within the fundamental diagram, which could reproduce aspects of the three-phase theory. This so-called average space gap model (ASGM) is based on the Nagel–Schreckenberg model with additional slow-to-start and anticipation rules. The anticipation rule takes into account the average space gap of multiple leading vehicles and conveys to the model its three-phase property. Due to the anticipation rule, ASGM can show the transition from free flow to synchronized flow. Due to the slow-to-start rule, ASGM can show the spontaneous wide moving jam emerges in the synchronized flow. Simulations are carried out for periodic and open boundary conditions. Under periodic boundary condition, the fundamental diagram, and the properties of synchronized flow are studied. Under open boundary condition, different congested patterns induced by an on-ramp are analyzed. We found that the ASGM produces the same spatiotemporal dynamics as many of the more complex three-phase models. Due to its simplicity and its close relation to conventional slow-to-start models, this model can shed light on the relation between ‘two-phase’ and three-phase models.     

Phase transition of traffic states with on-ramp

We study the phase transition on a highway in a modified anisotropic continuum model with an on-ramp, which is recently developed by Gupta and Katiyar (J. Phys. A: Math. Nucl. Gen. 38 (2005) 4069]. To investigate whether this model can describe several distinct traffic states that are identified from real-traffic data [Kerner and Rehborn, Phys. Rev. Lett. 79 (1997) 4030; Kerner, Phys. Rev. Lett. 81 (1998) 3797], we carry out numerical simulations with an open boundary condition. The observed transition between free flow and various types of congested flow such as localized clusters, stop-and-go traffic and different kinds of synchronized traffic flow is obtained by applying a triggering pulse through an on-ramp in our simulation.We present the phase diagram for three representative values of the upstream boundary flux and for the whole range of the on-ramp flux. Several states like pinned localized cluster, triggered stop-and-go, recurring hump state, the oscillatory congested traffic and the homogeneous congested traffic are observed in phase transition from free flow to traffic-jam state. The phase diagram for our model near on-ramp is consistent with the results obtained by Lee et al. [Phys. Rev. E 59(5) (1999) 5101]. The results suggest that the modified model is able to describe all the three phases of traffic-flow theory developed by Kerner [Physica A 333 (2004) 379].