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     

城市快速路系统的元胞自动机模型与分析

使用元胞自动机模型研究包含出入匝、主路和辅路的城市快速路系统的交通问题,为不同类型的路段定义了三种不同的换道规则.模拟结果表明,高入匝流量容易导致主路、匝道及其上游出现拥堵,高出匝流量容易使匝道出口车流与辅路内侧道车流发生冲突.入匝流量比较高时,主辅路为双车道的系统可以延缓交通拥堵和减少通行时间;当入匝流量较低时,双车道改善了单车道下辅路的通行状况. 关键词： 交通流 元胞自动机 换道规则 匝道     

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     

基于元胞自动机模型的上匝道合流处交替通行控制的研究

上海市高架道路的上匝道合流处率先实施了交替通行的控制策略.以Fukui和Ishibashi提出的FI元胞自动机交通流模型为基础，对实施该策略前后的上匝道合流处分别建立合理的交通流模型，并对交通流进行了数值模拟和分析.结果表明：当高架路主线和上匝道的来流车辆较多时，交替通行控制可以大大改善高架道路交通；当交通流稀疏时，实施控制前后交通流状况基本不发生变化. 关键词： 元胞自动机模型 上匝道合流处 交替通行控制 数值模拟     

双车道元胞自动机NS和WWH交通流混合模型的研究

考虑不同车辆的驾驶员有不同的驾驶方式和习惯，具体表现为不同的驾驶员采用适合自己行车特点的交通流模型在道路上驾车行驶，在一维元胞自动机交通流NS模型和WWH模型的基础上，建立了双车道元胞自动机NS和WWH交通流混合模型. 通过计算机模拟，给出了混合比例系数f_NS对混合交通流的速度-密度和流量-密度图以及车辆转道频率影响的结果. 关键词： 双车道 元胞自动机 混合交通流模型 计算机数值模拟     

双下匝道系统的交通流动态特征及其优化

利用多车道元胞自动机模型研究双下匝道系统的交通流动态演化特征.采用可变情报板来实现交通诱导,着重分析驾驶员选择目标匝道的决策行为及其对道路通行能力的影响.分别建立了无可变情报板的基本模型和有可变情报板的诱导模型.通过数值模拟,分别给出了相应的相图、道路通行能力、流量图和时空斑图,分析了进车概率、出车比例和出车道长度对交通行为的影响.通过对两个模型模拟结果的比较分析,发现当出车道长度较小而进车概率、出车比例都较大时,可变情报板的诱导信息能明显提高下游匝道的利用率,改善道路交通流状况,从而缓解交通拥堵.     

交通灯控制下城市主干道双车道多速元胞自动机交通流模型研究

提出一个城市主干道双车道多速元胞自动机交通流模型，此模型采用开放性 边界条件，在考虑诸多实际因素影响情况下，研究了主干道中车站的设置、交通灯绿信比对 车流量和车流速度的影响.计算机模拟所得到的基本图（流量 速度图）能较好地反映在交 通灯控制下城市主干道交通流真实状况. 关键词： 元胞自动机模型 交通流 主干道     

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     

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     

双向两车道混合车辆交通流的特性

在NaSch模型的基础上，制订了超车规则，建立了双向两车道混合车辆的元胞自动机交通流模型. 用计算机模拟了车道密度对称和不对称两种情况下不同参数的混合车辆交通流，得出了相应的速度、流量与密度关系的基本图. 经分析发现，双向两车道混合车辆交通状态可分为快车特性区、准慢车特性区和慢车特性区；两车道上车辆密度的不对称性对交通流有重要的影响. 关键词： 元胞自动机 交通流 混合车辆交通流     

Efficiency promotion for an on-ramp system based on intelligent transportation system information

<正>The effect of cars with intelligent transportation systems(ITSs) on traffic flow near an on-ramp is investigated by car-following simulations.By numerical simulations,the dependences of flux on the inflow rate are investigated for various proportions of cars with ITSs.The phase diagrams as well as the spatiotemporal diagrams are presented to show different traffic flow states on the main road and the on-ramp.The results show that the saturated flux on the main road increases and the free flow region is enlarged with the increase of the proportion of cars with ITS.Interestingly,the congested regions of the main road disappear completely when the proportion is larger than a critical value.Further investigation shows that the capacity of the on-ramp system can be promoted by 13%by using the ITS information, and the saturated flux on the on-ramp can be kept at an appropriate value by adjusting the proportion of cars with ITS.     

The effect of restricted velocity in the two-lane on-ramp system

Usually there are multi-lane on the main road of the on-ramp system. The drivers may decelerate for more safety when they are near the on-ramp. In addition, the car velocity may be restricted according to the traffic regulation. In this paper, we study phenomenon using the cellular automata traffic flow model. We find that: (i) the phase diagram of the two-lane on-ramp system appears a new region, in which the traffic of the on-ramp reaches maximum flow. (ii) The introduction of restricted velocity region will decrease capacity of the on-ramp, but reduce the drastic velocity fluctuation near the on-ramp.     

Traffic behavior in the on-ramp system with signal controlling

In this paper, we investigate the on-ramp system on the highway using cellular automaton traffic model. Different from previous work, we introduce traffic signal to control the vehicle flows on the main road and the on-ramp. A method of signal controlling is presented, and the update rule in special road is given in detail according to the stimulation role of signal to the drivers. The simulation results show that, the phase diagram of on-ramp system is divided into three regions. The currents of the on-ramp system are discussed. Under the control role of traffic signal, the vehicle flows of the main road and the on-ramp can become orderly. The capacity of the system may keep a maximum value. In addition, the drastic velocity fluctuation is discussed near the on-ramp. A dangerous condition in Jiang et al. [Phys. Rev. E 66 (2002) 036104] can be effectively avoided.     

The effects of accelerating lane in the on-ramp system

Usually there is an accelerating lane as an on-ramp merges with the main road. How the length of this section and the traffic regulations influence the traffic behaviors has seldom been investigated. In this paper, we study this issue using the cellular automata traffic flow model. We find that (i) the permission of lane changing from main road to the accelerating lane will deteriorate the capacity of the road, hence it should be forbidden; (ii) when lane changing from main road to accelerating lane is forbidden, the introduction of an accelerating lane can improve the capacity of the on-ramp system.     

Combined bottleneck effect of on-ramp and bus stop in a cellular automaton model

The combined bottleneck effect is investigated by modeling traffic systems with an on-ramp and a nearby bus stop in a two-lane cellular automaton model. Two cases, i.e. the bus stop locates in the downstream section of the on-ramp and the bus stop locates in the upstream section of the on-ramp, are considered separately. The upstream flux and downstream flux of the main road, as well as the on-ramp flux are analysed in detail, with respect to the entering probabilities and the distance between the on-ramp and the bus stop. It is found that the combination of the two bottlenecks causes the capacity to drop off, because the vehicles entering the main road from the on-ramp would interweave with the stopping (pulling-out) buses in the downstream (upstream) case. The traffic conflict in the former case is much heavier than that in the latter, causing the downstream main road to be utilized inefficiently. This suggests that the bus stop should be set in the upstream section of the on-ramp to enhance the capacity. The fluxes both on the main road and on the on-ramp vary with the distance between the two bottlenecks in both cases. However, the effects of distance disappear gradually at large distances. These findings might give some guidance to traffic optimization and management.     

考虑自适应巡航车辆影响的上匝道系统混合交通流模型

在考虑自适应巡航(adaptive cruise control, ACC)车辆的交通流模型的基础上, 建立了考虑ACC车辆影响的上匝道系统混合交通流模型, 研究ACC车辆引入对上匝道交通系统交通流的影响. 为了描述ACC车辆和手动驾驶车辆在交通流运行中的差异, 分别构建了基于常车头时距原则的ACC 车辆跟驰子模型和手动驾驶车辆MCD元胞自动机子模型; 基于上匝道车辆合流驶入主线的需求, 建立了换道子模型, 引入了表征驾驶员换道心理的参数λ. 通过对混合交通流模型进行数值模拟发现, ACC车辆的混入可以有效改善上匝道系统交通流的运行, 降低合流等事件对于交通流运行的影响, 抑制交通拥堵的时空范围及拥堵强度, 提高交通流的平均速度和流量. 此外在混合交通流模型中, ACC车辆期望车头时距H_d的减小与换道心理参数λ 的增大均可以提高混合交通流运行的速度和流量, 而合流区长度l_w对混合交通流影响则因上匝道车辆驶入概率的不同而存在差异.     

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.     

提高道路交通系统的驾驶安全

道路交通系统是一个复杂的系统，其中包含了人的直接参与。在该系统中，人的因素起了重要的作用。本文中，在道路系统路面的某一点设计了一种类型控制信号，该点被称为信号点。在控制信号的作用下，当车辆经过信号点的时候，车辆需要降低速度。其目的在于能够通过控制信号控制交通流的状态，使其由无序变为有序，从而提高道路系统的交通安全。应用双车道的确定性NaSch模型进行仿真模拟，结果表明不仅交通流的状态能够由无序变为有序，而且交通流的状态是安全的。