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.     

平面环行交叉路口交通流的研究

从道路结构出发,对具有内、外环道的平面环形交叉路口建立了具有多个道路瓶颈的元胞自动机模型,对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,环形交叉路口的内环道中与入环车道接壤处是最容易发生阻塞的地方,内环道中车辆之间的非线性相互作用的效应随刹车概率的增大而增强,流量随之减小;而转向概率的增加有助于提高系统交通流量. 关键词： 平面环形交叉路口 元胞自动机模型 瓶颈 自组织     

The CA model for traffic-flow at the grade roundabout crossing

The cellular automaton model is suggested to describe the traffic-flow at the grade roundabout crossing. After the simulation with computer, the fundamental properties of this model have been revealed. Analysing this kind of road structure, this paper transforms the grade roundabout crossing with inner-roundabout-lane and outer-roundabout-lane into a configuration with many bottlenecks. Because of the self-organization, the traffic flow remains unblocked under a certain vehicle density. Some results of the simulation are close to the actual design parameter.     

A study on the effects of the transit parking time on traffic flow based on cellular automata theory

This paper mainly deals with the effects of transit stops on vehicle speeds and conversion lane numbers in a mixed traffic lane.Based on thorough research of traffic flow and cellular automata theory,it calibrates the cellular length and the running speed.Also,a cellular automata model for mixed traffic flow on a two-lane system under a periodic boundary condition is presented herewith,which also takes into consideration the harbour-shaped transit stop as well.By means of computer simulation,the article also studies the effects of bus parking time on the traffic volume,the transit speed and the fast lane speed at the same time.The results demonstrate that,with the increase of the bus parking time,the traffic volume of the transit stop and the transit speed decrease while the fast lane speed increases.This result could help calculate the transit delay correctly and make arrangements for transit routes reasonably and scientifically.     

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     

A new lattice model of traffic flow with the anticipation effect of potential lane changing

A new lattice model of traffic flow is presented by taking into account the anticipation of potential lane changing on front site on single lane. The stability condition of the extended model is obtained by using the linear stability theory. The modified KdV equation near the critical point is constructed and solved through nonlinear analysis. And the phase space of traffic flow in the density-sensitivity space could be divided into three regions: stable, metastable and unstable ones, respectively. Numerical simulation also shows that the consideration of lane changing probability in lattice model can stabilize traffic flow, which implies that the new consideration has an important effect on traffic flow in lattice models.     

A cellular automata model for urban traffic with multiple roundabouts

Urban transportation with multiple roundabouts is facing significant challenges such as traffic congestion, gridlock and traffic accidents. In order to understand these behaviors, we propose a two-dimensional cellular automata (CA) model, where all streets are two-way, with one lane in each direction. To allow the turning movement, a roundabout is designed for each intersection where four roads meet. The distance between each pair of roundabouts is configured with the parameter K while the turning behavior of drivers is modeled by a parameter γ. To study the impact of these different parameters on the urban traffic, several traffic metrics are considered such as traffic flow, average velocity, accident probability and waiting time at the entrance of roundabout. Our simulation results show that the urban traffic is in free flow state when the vehicle’s density is low enough. However, when the density exceeds a critical density ρ_c, the urban traffic will be in gridlock state whenever γ is nonzero. In the case where $\gamma =0,$ the urban traffic presents a phase transition between free flow and congested state. Furthermore, detailed analysis of the traffic metrics shows that the model parameters (γ, K) have a significant effects on urban traffic dynamics.     

敏感换道对下匝道系统交通流的影响

在NaSh模型基础上,充分考虑驾驶员在匝口指示牌的诱导作用下驾驶方式的变化,定义了车辆在匝口上游的换道、直行驾驶规则,提出了敏感换道的元胞自动机下匝道交通流模型. 通过计算机数值模拟,结果表明：敏感换道过程能减少直行车道上的转出车辆比例,对非必要的换道行为有明显的抑制作用,且随敏感换道区长度增加,该作用越明显;匝口提示位置并非越长越好,系统转出车辆比例越小,系统所需的最佳敏感换道区长度越短. 工程设计中根据转出车辆比例选取一个适宜距离安放匝口指示牌,能有效增加系统流量和临界加入概率. 关键词： 交通流 元胞自动机 驾驶方式 计算机数值模拟     

考虑驾驶方式改变的一维元胞自动机交通流模型

在一维元胞自动机交通流WWH模型和SDNS模型的基础上,建立了考虑驾驶方式改变的元胞自动机模型（Change-CA模型）.具体描述为驾驶员可根据交通环境选择不同的驾驶方式在道路上驾车行驶,以各自的演化规则进行状态更新,同时定义了驾驶方式更新原则.通过计算机数值模拟,发现驾驶方式可变时,模型模拟得到的混合交通流流量较大;保守型驾驶方式对交通流变化的影响随改变概率增大而减少.并且在演化过程中,驾驶方式改变频率的变化趋势与改变概率、安全概率密切相关.与NS模型和SDNS模型相比,Change-CA模型减少了车流 关键词： 交通流 元胞自动机 驾驶方式 计算机数值模拟     

A new lattice model of traffic flow with the consideration of the traffic interruption probability

In this paper, we present a new lattice model which involves the effects of traffic interruption probability to describe the traffic flow on single lane freeways. The stability condition of the new model is obtained by the linear stability analysis and the modified Korteweg-de Vries (KdV) equation is derived through nonlinear analysis. Thus, the space will be divided into three regions: stable, metastable and unstable. The simulation results also show that the traffic interruption probability could stabilize traffic flow.     

Effect of road structure on the capacity of a signalized road intersection

In this paper, we use the stochastic Nagel--Schreckenberg (NaSch) model to investigate the influence of a special right-turning lane connecting two main roads on the capacity of a signalized road intersection. It is found that the magnitude of right-turning traffic flow and the linking position of the special right-turning lane can greatly influence the capacity of the signalized road intersection. The relation between traffic flow and entering probability for different distances between the entrance (exit) of the special right-turning lane and the road intersection is simulated and analysed. The corresponding spatiotemporal pattern and phase diagram on different sections of the main road are given under the condition of close proximity to the signalized road intersection, stop-and-go traffic occur and obstruct the intersection. On the contrary, unchanged flux is maintained as the distance exceeds a critical values. All the studies indicate that setting a special right-turning lane by choosing a suitable location near a signalized road intersection can relieve the load of current traffic on the main road and maintain traffic flow.     

Intelligent driving in traffic systems with partial lane discipline

It is a most common notion in traffic theory that driving in lanes and keeping lane changes to a minimum leads to smooth and laminar traffic flow, and hence to increased traffic capacity. On the other hand, there exist persistent vehicular traffic systems that are characterised by habitual disregarding of lane markings, and partial or complete loss of laminar traffic flow. Here, we explore the stability of such systems through a microscopic traffic flow model, where the degree of lane-discipline is taken as a variable, represented by the fraction of drivers that disregard lane markings completely. The results show that lane-free traffic may win over completely ordered traffic at high densities, and that partially ordered traffic leads to the poorest overall flow, while not considering the crash probability. Partial order in a lane-free system is similar to partial disorder in a lane-disciplined system in that both lead to decreased traffic capacity. This could explain the reason why standard enforcement methods, which rely on continuous increase of order, often fail to incur order to lane-free traffic systems. The results also provide an insight into the cooperative phenomena in open systems with self-driven particles.     

Numerical study of urban traffic flow with dedicated bus lane and intermittent bus lane

Based on the cellular automaton traffic flow model and the concept of public transport priority, a two-lane traffic model with an intermittent bus lane is proposed and the properties of urban traffic flow are studied. The cases of traffic with a dedicated bus lane (DBL), an intermittent bus lane (IBL) and an ordinary two-lane traffic are simulated, and comparisons in the form of the fundamental diagrams and the velocity-density profiles are made between them. It is shown that the DBL has the advantage of freeing buses from traffic interference and also has the disadvantage of disrupting traffic, the IBL is more efficient in improving the bus flow than ordinary two-lane traffic and maintaining the car flow at a higher level at the same time than the DBL, while the ordinary two-lane traffic suppresses public transportation and is not advantageous in easing urban traffic congestion. Also it is indicated that the DBL is only appropriate for low traffic flow in a two-lane traffic system, and this limitation can be partly overcome by opening the bus lane to general traffic intermittently when the bus lane is not in use by buses.     

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     

Traffic bottleneck characteristics caused by the reduction of lanes in an optimal velocity model

In this paper, the lane reduction bottleneck is investigated using the optimal velocity model, in which two kinds of vehicles (fast and slow) are introduced. The asymmetric lane changing rules in the slowdown section and the lane squeezing behaviors at the bottleneck are taken into account. Under the periodic boundary condition, the numerical simulations are performed. The traffic states change with increasing density. And an interesting phenomenon of ratio inversion appears. When the current saturates, the headway and velocity discontinuously vary with the position. In addition, traffic patterns and the phase transition points depend greatly on the speed limit and the length of the slowdown section.     

Traffic flow velocity disturbance characteristics and control strategy at the bottleneck of expressway

In the three-phase traffic flow studies, the traffic flow characteristic at the bottleneck section is a hot spot in the academic field. The controversy about the characteristics of the synchronized flow at bottleneck is also the main contradiction between the three-phase traffic flow theory and the traditional traffic flow theory. Under the framework of three-phase traffic flow theory, this paper takes the on-ramp as an example to discuss the traffic flow characteristics at the bottleneck section.In particular, this paper mainly conducts the micro-analysis to the effect of lane change under the two lane conditions, as well as the effect of the on-ramp on the main line traffic flow. It is found that when the main road flow is low, the greater the on-ramp inflow rate, the higher the average speed of the whole road section. As the probability of vehicles entering from the on-ramp increases, the flow and the average speed of the main road are gradually stabilized, and then the on-ramp inflow vehicles no longer have a significant impact on the traffic flow. In addition, this paper focuses on the velocity disturbance generated at the on-ramp, and proposes the corresponding on-ramp control strategy based on it, and the simulation verified that the control strategy can reasonably control the traffic flow by the on-ramp, which can meet the control strategy requirements to some extent.     

两车道交通流耦合格子模型与数值仿真

考虑两车道耦合效应的影响和换道效应,提出了改进的两车道交通流耦合格子模型.同时,改进了换道时的流量转移率,这样更符合实际交通情况.通过线性稳定性分析,得到了改进模型的稳定性条件.数值模拟结果也表明,模型通过考虑耦合作用信息,更好地再现了换道情况,同时也表明两车道间的耦合效应对两车道交通流存在不可忽视的影响.     

Continuum modeling for two-lane traffic flow with consideration of the traffic interruption probability

Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour,this paper establishes a new two-lane microscopic car-following model.Based on this microscopic model,a new macroscopic model was deduced by the relevance relation of microscopic and macroscopic scale parameters for the two-lane traffic flow.Terms related to lane change are added into the continuity equations and velocity dynamic equations to investigate the lane change rate.Numerical results verify that the proposed model can be efficiently used to reflect the effect of the probability of traffic interruption on the shock,rarefaction wave and lane change behaviour on two-lane freeways.The model has also been applied in reproducing some complex traffic phenomena caused by traffic accident interruption.     

基于改进格子气模型的对向行人流分层现象的随机性研究

在考虑行人视野范围的随机偏走格子气模型基础上, 引入行人对前方开阔区域的移动偏好特性, 提出改进的格子气模型, 对通道内对向行人流进行仿真研究. 模型再现了对向行人流在不同密度下出现的3种演化过程, 发现了行人密度与对向行人流分层现象的形成具有随机性, 以及统计了概率的变化趋势, 同时分析了分层现象形成概率与系统几何尺寸参数、移动强度参数、右行人流比例参数和视野范围参数等的关系. 分析结果表明, 改进的模型能够再现实际低密度下对向行人流不会出现分层现象的特性. 根据分层形成的概率, 可将对向行人流的密度分为5个区间, 不同区间的行人流演化过程各有差异. 模型和分析结果对理解对向行人流的动态演化过程, 提高通道内对向行人流的走行效率有一定帮助.