Two-lane traffic simulations with a blockage induced by an accident car

Based on the two-lane traffic model proposed by Chowdhury et al., a highway traffic model with a blockage induced by an accident car is proposed, in which both symmetric lane changing rules and asymmetric lane changing rules are adopted. The fundamental diagrams and spatial-temporal profiles are presented after the numerical simulation and the jam transition is studied. It is shown that the accident car not only causes a local jam behind the accident car, but also causes vehicles to cluster in the bypass lane. The asymmetric lane changing rules are more advantageous in reducing the local jam than the symmetric lane changing rules when the accident car is in the right lane, and the symmetric lane changing rules are superior when the accident car is in the left lane. Furthermore the curves of lane-changing frequency against the total density are given. It is found that the vehicles will change lane more frequently when traffic is inhomogeneous with different types of vehicle or with an accident car.     

Cellular Automaton Models of Highway Traffic Flow Considering Lane-Control and Speed-Control

As two kinds of management modes of highway traffic control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highway system with two opposing directions under the above two modes are established considering car and truck mixed running. Through computer numerical simulating, the fundamental diagrams with different parameters are obtained, and after the analysis of density-flux diagrams, the variation discipline of flux with traffic density under different control models is gained. The results indicate that, compared with lane-control, utilization ratio of road can be further improved with speed-control when the truck number increases. The research result is of great significance for reasonable providing theoretical guidance for highway traffic control.     

决定论性逐步加速交通流模型的渐近稳态行为

研究Nagel-Schreckenberg(NS)交通流元胞自动机模型在不考虑车辆随机延迟情况下的决定论性模型的基本图,即渐近稳态的车流平均速度作为车辆密度的函数关系．证明决定论性NS模型,在车流的自组织作用下,其渐近稳态的基本图,与决定论性Fukui-Ishibashi(FI)交通流模型的基本图完全相同．这个结果表明,若把FI交通流模型中的车辆突然加速方式（即车辆速度可以在仅仅一个时步内加速到其最高速限M或前方空距所允许的最大速度）,改变为车辆逐步加速方式（车辆速度在每一时步中最多仅能增加一个速度单位）,则车辆的自组织相互作用,并不会改变其车流的长时间渐近稳态行为． 关键词：     

Traffic dispersion induced by noise in off-lattice model

We study the dispersion of vehicles induced by speed fluctuation on a single-lane highway under open boundary. We extend the cellular automaton model on one-dimensional lattice to the real-variable model on off-lattice (continuous-in space model) in order to take into account the fluctuation of vehicular speed. Vehicles extend over the highway when moving forward. The characteristics of traffic dispersion are derived. It is shown that vehicular traffic exhibits scaling property. When a vehicle accelerates for following the vehicle ahead, vehicles move forming a cluster without dispersion. The relationship between the width of vehicular cluster and acceleration rate is clarified.     

Earthquake model describes traffic jams caused by imperfect driving styles

The wide modeling potential of the classical spring-block type system is illustrated by an interdisciplinary application. A simple one-dimensional spring-block chain with asymmetric spring forces is used to model idealized single-lane highway traffic and the emergence of phantom traffic jams. Based on the stop-time statistics of one car in the row, a proper order parameter is defined. By extensive computer simulations the parameter space of the model is explored, analyzed and interpreted. Existence of free and congested flow phases is confirmed and the transition between them is analyzed.     

高速车随机延迟逐步加速交通流元胞自动机模型

提出介于Nagel-Schreckenberg(NS)模型和Fukui-Ishibashi(FI)模型之间的一种新的一维交通流元胞自动机模型. 此模型采用NS模型中的车辆逐步加速方式,和FI模型中的仅最大速车可随机减速的车辆延迟方式.证明新模型的基本图,即车流渐近稳态的平均速度与道路上的车辆密度之间的函数关系与FI模型的完全相同.这也就是说,只允许最高速车辆可发生延迟的FI交通流模型,如果将其突然无限制加速方式(车辆可在一个时步内从零速加速到最高速限M或车头距离所允许的最大速度),改变为车辆的逐步有限加速 关键词： 交通流 元胞自动机模型 相变基本图 Nagel-Schreckenberg模型 Fukui-Ishibashi模型     

公路交通噪声阈限值的分析研究

本文采用客观测量和主观评价相结合的方法研究公路交通噪声对人的影响。通过研究，求得了公路交通噪声扰民的容忍阈值，分析了比较了公路交通噪声各种客观评价量与人的主观评价量的之间的相互关系。     

高速跟驰交通流动力学模型研究

为研究道路交通中的高速跟驰物理现象,针对高速跟驰车辆特点,综合考虑了驾驶员换道决策行为以及随机慢化等因素,结合前景理论等方法,提出了一种用于模拟道路交通流中高速跟驰物理现象的动力学模型(简称HCCA模型).通过计算机数值模拟,研究了高速跟驰交通流物理现象演化机理及高速跟驰特性.结果表明:与对称的双车道元胞自动机动力学模型相比,本文建立的HCCA动力学模型能够再现道路高速跟驰物理现象,并得到了道路小间距高速跟驰率超过7%的结果与实测结果相符合,最后模拟得到了丰富的交通物理现象,再现了自由流、同步流及运动阻塞等复杂交通物理现象.     

Spring-block model for a single-lane highway traffic

A simple one-dimensional spring-block chain with asymmetric interactions is considered to model an idealized single-lane highway traffic. The main elements of the system are blocks (modeling cars), springs with unidirectional interactions (modeling distance-keeping interactions between neighbors), static and kinetic friction (modeling inertia of drivers and cars) and spatiotemporal disorder in the values of these friction forces (modeling differences in the driving attitudes). The traveling chain of cars correspond to the dragged spring-block system. Contrary to most of the studies in the field of highway traffic here we focus on a measure characteristic for one car in the row. Our statistical analysis for the spring-block chain predicts a non-trivial and rich complex behavior. As a function of the disorder level in the system a dynamic phase-transition is observed. For low disorder levels uncorrelated slidings of blocks are revealed while for high disorder levels correlated avalanches dominates.     

Extreme fluctuation events in a simple high-density traffic model

We revisit a simple car-following model adapting it for simulating high-density traffic dynamics. Simulations in continuum space and discrete time are presented for the case of a single traffic lane, using periodic boundary conditions. The model parameters are fitted to empirical data for the mean car speed versus car density for densities higher than . The time evolution of the car ensemble is studied upon application of different types of random perturbations yielding strong speed fluctuations in all cases, the latter characterized by probability distribution functions displaying fat tails. We attempt to study the phenomenon of stop-and-go along the lane in the absence of perturbations by assuming a stopping cutoff speed, and find the resulting behavior of the ensemble both in space and time.     

Second-order phase transition in two-dimensional cellular automaton model of traffic flow containing road sections

Two-dimensional cellular automaton model has been broadly researched for traffic flow, as it reveals the main characteristics of the traffic networks in cities. Based on the BML models, a first-order phase transition occurs between the low-density moving phase in which all cars move at maximal speed and the high-density jammed phase in which all cars are stopped. However, it is not a physical result of a realistic system. We propose a new traffic rule in a two-dimensional traffic flow model containing road sections, which reflects that a car cannot enter into a road crossing if the road section in front of the crossing is occupied by another car. The simulation results reveal a second-order phase transition that separates the free flow phase from the jammed phase. In this way the system will not be entirely jammed (“don’t block the box” as in New York City).     

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.     

基于LED照明灯光的可见光室内停车场定位导航系统

室内停车场是静态交通的一个重要组成部分,由于缺乏有效的室内定位技术,目前存在着泊车导航以及反向寻车困难的问题。提出一种基于LED照明灯光的可见光室内停车场定位导航系统,实现了面向车辆的停车位引导和面向行人的反向寻车导航,具有定位速度快、定位精度高和"照明定位两用"的优势。实验结果及现场测试表明:该系统定位精度可达到7.5 cm,可支持车辆或行人在时速达17 km/h下的实时定位导航。     

考虑意外事件对交通流影响的元胞自动机交通流模型

在NaSh模型的基础上,考虑交通事故和养护路段等意外事件对高速公路交通流的影响,建立了有意外事件影响的在车道管制下的高速公路交通流元胞自动机模型,并进行数值模拟. 研究发现:意外事件对高速公路交通流有明显影响,并且意外事件对交通流的影响在某一密度值范围内尤其明显,且意外事件堵塞点在第一车道比在第二车道对交通流的影响小;同时,在该密度值范围内,意外事件堵塞时间和堵塞路段长度越长,对交通流的影响就越大. 关键词： 元胞自动机 交通流 意外事件     

高速桥梁瓶颈模型属性的研究

针对现实中桥梁形成的交通流瓶颈，建立了一个基于元胞自动机交通流桥梁瓶颈模型. 在周期性边界条件下，将系统的状态分成六“相”，利用平均场理论和决定性NS模型的结果，得到每条车道上的密度关系. 分析的理论值与计算机数值模拟结果符合得很好. 关键词： 元胞自动机模型 桥梁瓶颈 决定性NS模型 选择概率     

高速公路入匝控制的一个元胞自动机模型

采用元胞自动机模型研究高速公路入匝控制问题. 利用主路上测定区域内的车辆数设计了一种新型入匝信号控制方法,模拟分析了各种参数对主路和匝道交通的影响. 结果表明,设置匝道信号灯可以保证主路交通畅通,尤其是匝道处的车辆到达率比较高时效果非常明显. 测定区域位置、抑制入匝车流量以及并道区长度的不同组合可以导致不同的主路和匝道交通流,合理搭配这三个参数可以兼顾主路和匝道的流量和通行时间.测定区域应该设置在并道段前或并道段上游的适当位置. 关键词： 交通流 元胞自动机 入匝控制 并道规则     

Bunching and transition of vehicles controlled by a sequence of traffic lights

We study the dynamical behavior of many vehicles with different desired velocities, moving through a sequence of traffic lights on a single-lane highway, where the traffic lights turn on and off periodically with the synchronized strategy. The dynamics of vehicular traffic controlled by traffic lights is described in terms of the nonlinear maps. For specific values of cycle time, the group (cluster) of vehicles exhibits the bunching without extending over the highway. It is found that two types of traffic states appear: the one is the bunching traffic and the other is the extended traffic. In the bunching traffic, all vehicles move together with the same tour time, while vehicles spread over the highway in the extended traffic. The dynamical transition between two traffic states occurs at specific values of cycle time. The phase diagram (region map) is presented.     

高速公路交通流元胞自动机模型的一种统计平均解耦处理

对于高速公路交通流的一维元胞自动机模型，提出一种从微观格点状态更新规则出发，经过逐步的统计系综平均和截断退耦近似处理，推导宏观演化规律，从而获得描述车流稳态平均速度与车辆密度之间关系的基本图曲线的平均场方程方法.宏观演化规律表现为相继两个时刻车流平均速度的一个非线性映射.平均场论可以作为这一非线性映射的吸引子得到.将此法应用于Fukui-Ishibashi建议的高速运动车模型，计算表明：在单辆车最大速度为M的情形，可以采用截断退耦到仅保留M+1格点耦合的近似法计算空间关联函数.对于不考虑随机减速的决定论模     

The annual average sound level of road traffic noise estimated from the speed-flow diagram

The speed-flow diagram correlates traffic speed and traffic flow on a road. The presented method enables estimation of the annual average sound level of the road traffic noise when the characteristics of the diagram are available: traffic flow capacity, free traffic speed, and traffic capacity speed (Fig. 1). Bunches of vehicles decrease the traffic speed and traffic noise.     

Modeling U-turn traffic flow

Median U-turns are sometimes installed to improve the traffic flow at busy intersections by eliminating left turns. Using a microscopic traffic model, we confirmed the presence of transitions from free flow to congested flow with increasing car inflow density. In addition, our proposed rules inside a U-turn curve, which accounted for safety issues and an asymmetric lane changing behavior (outer-to-inner vs. inner-to-outer lane transitions), predicted the speed distribution of cars after the U-turn curve. We found that U-turn curves installed for improving traffic flow at busy intersections produced their desired effects only when there is minimal interaction between cars.