共查询到19条相似文献,搜索用时 187 毫秒
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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 相似文献
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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: 相似文献
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车辆的横向偏移现象在现实的交通流中广泛存在, 交通瓶颈处的横向偏移现象往往更加显著. 车辆间横纵向的运动相互干扰, 使得瓶颈交通流组织十分混乱, 通行能力受到显著影响. 为了研究瓶颈处车辆横纵向行为规律及其对交通流的影响, 提出一个考虑横向偏移特征的车辆行为模型: 通过引入目标转向角概念,并结合经典优化速度模型, 给出了用于描述车辆的横纵向运动规律的运动方程, 同时通过分析车辆横向偏移特征, 制定了基于车辆行驶状态划分的目标转向角确定规则集. 数值模拟结果表明: 车辆的横向偏移会对交通流的运行产生影响, 在一定的横向偏移反应阈值下, 瓶颈处横向干扰于交通流的影响随着密度的增加而增加; 同时观察到了实际城市交通瓶颈的宏观及微观现象, 验证了模型的有效性.
关键词:
交通流
瓶颈
车辆行为
横向偏移特征 相似文献
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为了更加客观地描述实际的车辆跟驰行为, 在优化速度模型的基础上, 通过引入横向分离参数并提出超车期望和虚拟前车的概念, 建立了考虑横向分离与超车期望的车辆跟驰模型.对模型进行线性稳定性分析, 得到了模型稳定性条件, 发现车辆横向分离、超车期望和虚拟前车的位置的增加, 在车流密度较小、车速较快的情况下, 使得交通流稳定区域增大, 但在车流密度较大、车速较慢的情况下, 反而使得交通流稳定区域减小.数值模拟结果验证了模型稳定性分析的结果, 表明在交通瓶颈处等交通流密度较大、运行缓慢的区域, 为抑制交通拥堵, 应该限制车辆的横向偏移和超车行为的发生.
关键词:
交通流
车辆跟驰模型
横向分离
超车期望 相似文献
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从研究微观个体车辆行为出发,考虑车辆加速过程的不确定性,提出了随机计及相对速度的 交通流跟驰模型(SR-OV模型).对随机相对速度的跟驰模型的动力学方程进行稳定性分析,得 到与Bando跟驰模型不同的稳定性判据,其稳定性优于Bando模型.运用摄动理论分析交通过 程中密度波的变化,结果表明,在发生交通阻塞相变时,交通密度波以mKdV方程描述的扭结 -反扭结波演化.对随机相对速度跟驰模型进行数值模拟和分析,结果发现车流速度的变化小 于Bando模型的速度变化,而且与随机概率有关,当随机考虑相对速度的概率增大时,初始 的小扰动不会放大对车流产生影响,甚至长时间就消失,这与Bando模型完全不同.数值模拟 所得到的相图与解析解相符合,而且交通流稳定区域大于Bando模型.从车间距-速度演化图上 ,随着随机概率的增大,SR-OV模型在初始时存在的滞后现象,随着时间的增长,趋于稳定 状态后,滞后曲线收敛于一小区域,滞后效应被削弱.这完全不同于Bando模型,在Bando模 型中,滞后曲线由一点向外扩散,滞后曲线区域越来越大,车流趋于不稳定状态.
关键词:
交通流
跟驰模型
稳定性判据
相对速度 相似文献
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In this paper, the characteristics of synchronized traffic in mixed traffic flow are investigated based on the braking light model. By introducing the energy dissipation and the distribution of slowdown vehicles, the effects of the maximum velocity, the mixing ratio, and the length of vehicles on the synchronized flow are discussed. It is found that the maximum velocity plays a great role in the synchronized flow in mixed traffic. The energy dissipation and the distribution of slowdown vehicles in the synchronized flow region are greatly different from those in free flow and a traffic jamming region. When all of vehicles have the same maximum velocity with V max > 15, the mixed traffic significantly displays synchronized flow, which has been demonstrated by the relation between flow rate and occupancy and estimation of the cross-correlation function. Moreover, the energy dissipation in the synchronized flow region does not increase with occupancy. The distribution of slowdown vehicles shows a changeless platform in the synchronized flow region. This is an interesting phenomenon. It helps to deeply understand the synchronized flow and greatly reduce the energy dissipation of traffic flow. 相似文献
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Based on the Ishibashi and Fukui crossroad traffic flow model [Y. Ishibashi and M. Fukui. J. Phys. Soc. Japan. 70 (2001) 2793], mixed traffic flow (i.e., the fast and slow vehicles with different maximum velocities are mixed) is investigated in this work. According to the numerical simulation results and the principle for constructing the phase diagram, phase diagrams for mixed traffic flow are constructed. It is noted that the topology of these phase diagrams is similar to that of phase diagrams for homogeneous vehicles (which refers to slow vehicles only). From the phase diagrams, it is evident that mixed traffic flow is influenced by the mixing rate f (fraction of slow and fast vehicles) in regions II and V, but not in other regions. Although a mixture of fast and slow vehicles is introduced in the crossroad traffic flow model, the separation between phases in the phase diagrams remains linear. For a given q (the vehicle density on the northbound road), one flow plateau appears in regions IIx or IVy, while two maximum flow plateaus appear in region V in each of the phase diagrams. The maximum flow values in region V reflect the maximum traffic capacity for the traffic system as defined in this work. Since mixed traffic flow is a common phenomenon in real traffic, this work may offer help in real traffic simulations and traffic management. 相似文献
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针对传统车辆和协同自适应巡航控制(cooperative adaptive cruise control,CACC)车辆构成的异质交通流,研究其稳定性与基本图模型.应用实车测试验证的CACC模型和智能驾驶员模型(intelligent driver model)分别作为CACC车辆和传统车辆的跟驰模型,建立异质流稳定性解析框架,研究不同平衡态速度、不同CACC车辆比例时的异质流稳定性.推导异质流基本图模型,并进行数值仿真实验.研究结果表明,在传统车辆稳定的速度范围,异质流处于稳定状态.在传统车辆不稳定的速度范围,CACC车辆比例增加以及平衡态速度远离9.6—18.6 m/s速度范围,均能够改善异质流的不稳定性.通行能力随着CACC车辆比例的增加而提高.此外,CACC模型的期望车间时距越大,异质流稳定域越大,但通行能力降低.因此,恒定车间时距CACC控制策略下的期望车间时距取值应权衡异质流稳定域和通行能力两个方面的影响. 相似文献
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To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a car-following model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, thetemporal-spatial dynamics, and the velocity evolution are investigated in detail. The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover,non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles. 相似文献
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Analysis of the influence of occupation rate of public transit vehicles on mixing traffic flow in a two-lane system
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Based on the existing classical cellular automaton model of traffic
flow, a cellular automaton traffic model with
different-maximum-speed vehicles mixed on a single lane is proposed,
in which public transit and harbour-shaped bus stops are
taken into consideration. Parameters such as length of cellular
automaton, operation speed and random slow mechanism are
re-demarcated. A harbour-shaped bus stop is set up and the vehicle changing
lane regulation is changed. Through computer simulation, the
influence of occupation rate of public transit vehicles on mixed
traffic flow and traffic capacity is analysed. The results show that
a public transport system can ease urban traffic congestion
but creates new jams at the same time, and that the influence of
occupation rate of public transit vehicles on traffic capacity is
considerable. To develop urban traffic, attention should be paid
to the occupation rate of public transit vehicles and traffic
development in a haphazard way should be strictly avoided. 相似文献
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Using the cellular automaton traffic flow model, we investigate an unsignalized intersection which consists of two perpendicular one-lane roads. Both the roads cross at a point and the intersecting roads are cyclic. Each vehicle may pass or occupy the intersection where all the vehicles on both roads are not allowed to turn. Different from Ishibashi and Fukui’s studies in which the update is carried out for both roads in turn, the parallel update is proposed and its detailed rules are presented in our model. In this work, the cases of different maximum vehicle velocities on both roads are considered. Based on simulation results and the principle for constructing phase diagrams, phase diagrams are mapped out and their specific flow formulas for all the regions in the phase diagrams are obtained for various vehicle densities, which are seldom done in previous studies. One also finds that the topology of phase diagrams depends on the update rules of eastbound and northbound roads and their maximum velocities of vehicles. 相似文献