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1.
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 ρc, the urban traffic will be in gridlock state whenever γ is nonzero. In the case where 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. 相似文献
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Takashi Nagatani 《Physica A》2009,388(8):1673-1681
We present a cellular automaton (CA) model for vehicular traffic controlled by traffic lights. The CA model is not described by a set of rules, but is given by a simple difference equation. The vehicular motion varies highly with both signals’ characteristics and vehicular density. The dependence of tour time on both cycle time and vehicular density is clarified. In the dilute limit of vehicles, the vehicular motion is compared with that by the nonlinear-map model. The fundamental diagrams are derived numerically. It is shown that the fundamental diagram depends highly on the signals’ characteristics. The traffic states are shown for various values of cycle time in the fundamental diagram. We also study the effect of a slow vehicle on the traffic flow. 相似文献
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M.E. Fouladvand M. Nematollahi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):395-401
We propose a model for the intersection of two urban streets. The traffic status of the crossroads is controlled by a set
of traffic lights which periodically switch to red and green with a total period of T. Two different types of crossroads are discussed. The first one describes the intersection of two one-way streets, while
the second type models the intersection of a two-way street with an one-way street. We assume that the vehicles approach the
crossroads with constant rates in time which are taken as the model parameters. We optimize the traffic flow at the crossroads
by minimizing the total waiting time of the vehicles per cycle of the traffic light. This leads to the determination of the
optimum green-time allocated to each phase.
Received 19 October 2000 and Received in final form 25 May 2001 相似文献
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Takashi Nagatani 《Physics letters. A》2009,373(5):536-539
When a vehicle moves through a series of green lights with avoiding red signals in the traffic network, the travel time has a minimal value and the vehicle draws a characteristic trajectory. We study the trajectories (green-light paths) of a vehicle for various values of both cycle time and split at the synchronized and random-phase strategies. The trajectory depends highly on both signal's characteristics and control strategy. We clarify the dependence of green-light paths on both cycle time and split. At the random phase strategy, the vehicle draws a trajectory of the random walk. It is shown where the vehicle arrives if a driver selects the green-light path. 相似文献
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在一维交通流格子模型的基础上,分别提出考虑最近邻车和次近邻车以及考虑前、后近邻车相互作用进行车流优化的一维交通流格子模型.应用线性稳定性理论和非线性理论进行分析,得出车流的稳定性条件,并导出了描述交通阻塞相变的mKdV方程.用数值模拟验证了mKdV方程的解,数值模拟结果表明考虑最近邻车和次近邻车的优化车流能够增强车流稳定性,而考虑前、后近邻车的优化车流将使稳定性减小.
关键词:
交通流
交通相变
稳定判据
mKdV方程 相似文献
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In this paper, the optimal velocity model of traffic is extended to take into account the relative velocity. The stability and density waves for traffic flow are investigated analytically with the perturbation method. The stability criterion is derived by the linear stability analysis. It is shown that the triangular shock wave, soliton wave and kink wave appear respectively in our model for density waves in the three regions: stable, metastable and unstable regions. These correspond to the solutions of the Burgers equation, Korteweg-de Vries equation and modified Korteweg-de Vries equation. The analytical results are confirmed to be in good agreement with those of numerical simulation. All the results indicate that the interaction of a car with relative velocity can affect the stability of the traffic flow and raise critical density. 相似文献
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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 相似文献
10.
在分析应急车辆对城市道路交通流影响的基础上, 引入让行状态参数、警笛影响区域和强制换道安全距离等特征变量, 修改换道规则, 建立了多车道元胞自动机模型, 并进行数值模拟. 结果表明, 车道数量和混合车辆比例系数在低密度范围内影响车辆速度及换道次数, 警笛影响区域参数改变了一定范围内车辆的换道次数, 应急车辆强制换道安全距离参数主要影响应急车辆的速度及换道次数.研究发现, 应急车辆对低密度交通流的扰动现象明显, 其与社会车辆相互作用参数的设置使得交通流元胞自动机模型更接近应急条件下实际交通运行.
关键词:
交通流
元胞自动机
应急车辆 相似文献
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Through introducing a generalized optimal speed function to consider spatial position, slope grade and variable safe headway, the effect of slope in a single-lane highway on the traffic flow is investigated with the extended optimal speed model. The theoretical analysis and simulation results show that the flux of the whole road with the upgrade (or downgrade) increases linearly with density, saturates at a critical density, then maintains this saturated value in a certain density range and finally decreases with density. The value of saturated flux is equal to the maximum flux of the upgrade (or downgrade) without considering the slight influence of the driver's sensitivity. And the fundamental diagrams also depend on sensitivity, slope grade and slope length. The spatiotemporal pattern gives the segregation of different traffic phases caused by the rarefaction wave and the shock wave under a certain initial vehicle number. A comparison between the upgrade and the downgrade indicates that the value of saturated flux of the downgrade is larger than that of the upgrade under the same condition. This result is in accordance with the real traffic. 相似文献
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L. Yu Z.-K. Shi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):115-120
The car-following model of traffic flow is extended to
take into account the relative velocity. The stability condition
of this model is obtained by using linear stability theory. It is
shown that the stability of uniform traffic flow is improved by
considering the relative velocity. From nonlinear analysis, it is
shown that three different density waves, that is, the triangular
shock wave, soliton wave and kink-antikink wave, appear in the
stable, metastable and unstable regions of traffic flow
respectively. The three different density waves are described by
the nonlinear wave equations: the Burgers equation, Korteweg-de
Vries (KdV) equation and modified Korteweg-de Vries (mKdV)
equation, respectively. 相似文献
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针对受多种因素影响的复杂道路交通系统问题,基于颗粒动力学理论,结合传统的Lighthill-WhithamRichards物理模型,建立道路交通系统的流体物理模型,采用无网格粒子与网格相结合的方法进行数值仿真,并应用于典型道路交通问题的求解.在新模型中,将车辆比拟为硬颗粒,车辆的跟车比拟为颗粒间的碰撞相互作用,已知道路情况对驾驶员操作车辆的影响比拟为流-粒两相系统中的外部流体驱动力作用,不同车道间车辆的影响比拟为颗粒间的黏性作用,从而在颗粒动力学理论的基础上,推导建立了道路交通系统拟流体模型;引入光滑离散颗粒流体动力学(SDPH)对车辆系统模型进行离散,建立"SDPH车辆"与真实车辆之间的一一对应关系,再结合有限体积方法,对道路交通构建的双流体模型进行求解,建立求解交通流体物理模型的新型仿真方法.最后,采用所建立的模型和方法对车辆汇入以及机非混合对交通系统的影响过程进行了数值仿真,所得结果与实测值符合较好,表明新的模型和方法有效性好、可靠性高,为道路交通问题的解决提供了一条全新的途径. 相似文献
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We study the dynamical behavior of N vehicles with no passing, but are 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 dynamical model of N vehicles controlled by traffic lights is described in terms of coupled maps with three parameters. The motions of vehicles display a complex behavior, interacting with other vehicles through the sequence of traffic lights. Fluctuation of the leading vehicle is amplified to the following vehicles. The amplification of fluctuation changes with cycle time. The dynamical behavior of vehicles depends highly on their position of grouping vehicles. Signal traffic at a low density changes at specific values of cycle time. The complex dynamical transitions occur by varying three parameters. 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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