Lane changing analysis for two-lane traffic flow

In this paper, the two-lane traffic are studied by using the lane-changing rules in the car-following models. The simulation show that the frequent lane changing occurs when the lateral distance in car following activities is considered and it gives rise to oscillating waves. In contrast, if the lateral distance is not considered (or considered occasionally), the lane changing appears infrequently and soliton waves occurs. This implies that the stabilization mechanism no longer functions when the lane changing is permitted. Since the oscillating and soliton waves correspond to the unstable and metastable flow regimes, respectively, our study verifies that a phase transition may occur as a result of the lane changing. The project supported by the National Natural Science Foundation of China (70521001, 10404025, 10532060), the National Basic Research Program of China (2006CB705503) and the Research Grants Council of the Hong Kong Special Administrative Region (HKU7031/02E, HKU7187/05E). The English text was polished by Boyi Wang.     

A continuum traffic flow model with the consideration of coupling effect for two-lane freeways

A new higher-order continuum model is proposed by considering the coupling and lane changing effects of the vehicles on two adjacent lanes. A stability analysis of the proposed model provides the conditions that ensure its linear stability. Issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are also investigated with numerical experiments. The simulation results show that the proposed model is capable of providing explanations to some particular traffic phenomena commonly observable in real traffic flows.     

Continuum modeling for two-lane traffic flow

In this paper, we study the continuum modeling of traffic dynamics for two-lane freeways. A new dynamics model is proposed, which contains the speed gradient-based momentum equations derived from a car-following theory suited to two-lane traffic flow. The conditions for securing the linear stability of the new model are presented. Numerical tests are carried out and some nonequilibrium phenomena are observed, such as small disturbance instability, stop-and-go waves, local clusters and phase transition. The project supported by the National Natural Science Foundation of China (70521001) The English text was polished by Yunming Chen.     

考虑道路信息和转向灯的可换道BML模型

车辆换道是司机为获得更好行驶条件而采用的常见措施, 而转向灯对车辆换道行为有重要的指导作用. 本文在BML (Biham-Middleton-Levine)模型的基础上加以改进, 提出了综合考虑道路信息和前车转向灯影响的可换道BML模型. 当车辆无法前行时, 如满足换道条件, 则将道路信息(车道密度及平均速度)和转向灯影响量化为车辆换道概率, 确定车辆是否可以换道. 通过数值模拟, 研究了周期边界条件下车辆换道行为对有、无交通灯控制的两种BML模型发生相变的临界密度以及系统通行能力的影响. 模拟结果表明对于无交通灯BML模型, 引入换道规则可以明显提高系统发生相变的临界密度, 在较小尺度下该临界密度接近有交通灯BML模型, 换道效果明显, 并发现了一种新的局部拥堵和自由流的共存相, 讨论了该共存相的生成和演化机制. 在较高密度下局部阻塞将演化为全局拥堵; 对于有交通灯BML模型, 引入换道规则对系统发生相变的临界密度没有明显的影响, 但相变的过渡区域更窄. 这表明有交通灯时, 换道虽然可以改变局部交通特征, 但难以显著影响交通系统的全局特征.      

A cellular automaton model for a bridge traffic bottleneck

A cellular automaton (CA) model is proposed in this paper to analyze a bridge traffic bottleneck. The simulation results with this model show that there are several phase transitions in the traffic average density, velocity and flow for each lane under a periodic boundary condition. An unstable phase in the traffic average density and velocity for the upstream and downstream lanes of the bridge is shown in a range of initial traffic densities. The critical points of the phase transitions and the phenomenon of the unstable phase found in the simulation are also explained with the mean-field theory.The project supported by the National Natural Science Foundation of China(70371067 and 10347001), the Key Project of Chinese Ministry of Education(02115) and the New Century Talent Plan of Guangxi Province in China(2001204).The English text was polished by Ron Marshall.     

TDGL and mKdV equations for an extended car-following model

In this paper, we construct an improved car-following model by accounting for the effect of the optimal velocity difference and a two-velocity difference. The effect of this model is examined through the linear stability analysis. The TDGL equation and the mKdV equation are derived from nonlinear analysis. Then, the energy consumption and the stability in car-following models considering the optimal velocity difference and a two-velocity difference are discussed. Moreover, numerical simulation shows that the new model can improve the stability of traffic flow, which is consistent with the theoretical analysis.     

On the stability analysis of microscopic traffic car-following model: a case study

The stability analysis of the microscopic traffic car-following model is an important issue. The present paper systematically discusses the local stability and asymptotic stability of the car-following model; meanwhile, the corresponding Lyapunov stability is also proposed from the viewpoint of control. Moreover, taking the full velocity difference (FVD) car-following model as a case, the difference among the three stability analysis approaches and the simulation are conducted. Finally, the results reveal that it can improve the dynamic performance when keep the value of the gain factor k constant and increase the value of sensitivity coefficient of velocity difference λ; and so is it when it keeps the value of a sensitivity coefficient of velocity difference λ constant and increases the value of the gain factor k, while the value of the gain factor k is dominant in this process.     

A new car-following model with consideration of anticipation driving behavior

A new anticipation driving car-following (AD-CF) model is presented based on the effect of traffic anticipation in the real world. The model??s linear stability condition was obtained by applying the linear stability theory. Additionally, a modified Korteweg?Cde Vries (mKdV) equation was derived via nonlinear analysis to describe the propagating behavior of traffic density wave near the critical point. Good agreement between the simulation and the analytical results shows that the stability of traffic flow can be enhanced when the driver??s anticipation effects are considered.     

A Nonlinear Temporal Headway Model of Traffic Dynamics

In order to describe the dynamics of a group of road vehicles travelling in a single lane, car-following models attempt to mimic the interactions between individual vehicles where the behaviour of each vehicle is dependent upon the motion of the vehicle immediately ahead. In this paper we investigate a modified car-following model which features a new nonlinear term which attempts to adjust the inter-vehicle spacing to a certain desired value. In contrast to our earlier work, a desired time separation between vehicles is used rather than simply being a constant desired distance. In addition, we extend our previous work to include a non-zero driver vehicle reaction time, thus producing a more realistic mathematical model of congested road traffic. Numerical solution of the resulting coupled system of nonlinear delay differential equations is used to analyse the stability of the equilibrium solution to a periodic perturbation. For certain parameter values the post-transient response is a chaotic (non-periodic) oscillations consisting of a broad spectrum of frequency components. Such chaotic motion leads to highly complex dynamical behaviour which is inherently unpredictable. The model is analysed over a range of parameter values and, in each case, the nature of the response is indicated. In the case of a chaotic solution, the degree of chaos is estimated.     

An extended car-following model accounting for the honk effect and numerical tests

In this paper, an extended car-following model is proposed to simulate traffic flow by considering the honk effect. The stability condition of this model is obtained by using the linear stability analysis. The phase diagram shows that the honk effect plays an important role in improving the stabilization of traffic system. The mKdV equation near the critical point is derived to describe the evolution properties of traffic density waves by applying the reductive perturbation method. Furthermore, the numerical simulation is carried out to validate the analytical results and indicates that the traffic jam can be suppressed efficiently via taking into account the honk effect.     

ONE-DIMENSIONAL CELLULAR AUTOMATON MODEL OF TRAFFIC FLOW BASED ON CAR-FOLLOWING IDEA

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ,ｃｅｌｌｕｌａｒａｕｔｏｍａｔｏｎ (ＣＡ)ｍｏｄｅｌｓｈａｖｅａｔｔｒａｃｔｅｄｅｘｔｅｎｓｉｖｅａｔｔｅｎｔｉｏｎｉｎｔｈｅｓｔｕｄｙｏｆｔｒａｆｆｉｃｆｌｏｗ[1- 10 ].Ｓｉｎｃｅｔｈｅａｇｇｒｅｇａｔｉｏｎｏｆｖｅｈｉｃｌｅｓｉｎｔｒａｆｆｉｃｆｌｏｗｉｓａｃｔｕａｌｌｙａｄｉｓｃｒｅｔｅｓｙｓｔｅｍ ,ｉｔｉｓｃｏｎｖｅｎｉｅｎｔｔｏｄｅｓｃｒｉｂｅｓｕｃｈａｓｙｓｔｅｍｗｉｔｈＣＡｍｏｄｅｌｓ,ｗｈｉｃｈａｒｅｉｎｔｒｉｎｓｉｃａｌｌｙｄｉｓ…     

基于场力的驾驶员影响因素交通流动力学模型

为研究驾驶员行为对道路交通的定量影响, 针对驾驶员行为特点, 综合考虑了驾驶员受到的直接物理影响和间接心理影响、相对速度以及车辆自身特性等因素, 结合场力、图论等方法, 提出了一种用于模拟考虑驾驶员影响因素的元胞自动机交通流动力学模型(简称IDCA模型). 通过计算机数值模拟, 研究了考虑驾驶员影响因素下车流演化机理及不同驾驶员类型对道路交通流的影响. 结果表明: 与NaSch模型相比, 本文建立的IDCA模型能够模拟得到丰富的交通行为, 再现了同步流等交通现象, 从速度波动和车头间距波动分析得出IDCA模型下道路交通流具有更强的稳定性, 堵塞消融效率更高. 此外得到了由不同驾驶员类型按不同比例组成的混合交通流的密度-速度图和密度-流量图, 发现在道路相同中高密度下, 激进型驾驶员所占的比例越大, 车辆速度与交通流量越大, 交通流量随着保守型驾驶员比例的增加而降低. 最后模拟实现了车辆高速跟驰现象, 得到小间距高速跟驰率超过7%的结果与实测结果相符合.      

三车道宏观交通流模型和扰动演化的数值研究

随着城市交通设施的完善,多车道在城市高速路交通中变得比较普遍. 三车道的出现使车辆变道易于实现,这就增加了交通问题的复杂性. 采用宏观交通流理论,建立了一种允许车辆变道的单向三车道连续交通流模型,以及与之相容的差分离散格式. 数值模拟了初始密度、扰动强度、初始扰动范围等因素对扰动传播和发展演化的影响. 结果显示:扰动波的传播方向和传播速度主要由初始未扰动车流密度大小决定;初始扰动范围的大小对扰动波幅值变化的影响比较大;某一条车道发生的扰动是否会影响其他车道,则受初始车流密度和扰动强度大小两个条件影响;在中等密度多车道交通流中,扰动波的发展过程呈现出复杂的非线性特征,数值格式的选择比单车道更加困难.      

Relative velocity difference model for the car-following theory

To explore and evaluate the impacts of relative velocity difference (RVD) with memory on the dynamic characteristics and fuel economy of traffic flow in the intelligent transportation environment, we first analyze the linkage between RVD with different-step memory and the following car’s behaviors with the measured car-following (CF) data in cities by using the gray correlation analysis method and then present a RVD model based on the previous CF models in the literatures and calibrate it. Finally, we conduct several numerical simulations in the adaptive cruise control (ACC) strategy to explore how RVD with memory affects car’s velocity fluctuation and fuel consumptions, and find that the RVD model can describe the phase transition of traffic flow and estimate the evolution of traffic congestion, and that considering RVD with memory in modeling CF behaviors and designing the advanced ACC strategy can improve the stability and fuel economy of traffic flow.     

Modeling and simulation for microscopic traffic flow based on multiple headway, velocity and acceleration difference

A new car-following model termed as multiple headway, velocity, and acceleration difference (MHVAD) is proposed to describe the traffic phenomenon, which is a further extension of the existing model of full velocity difference (FVD) and full velocity and acceleration difference (FVAD). Based on the stability analysis, it is shown that the critical value of the sensitivity in the MHVAD model decreases and the stable region is apparently enlarged, compared with the FVD model and other previous models. At the end, the simulation results demonstrate that the dynamic performance of the proposed MHVAD model is better than that of the FVD and FVAD models.     

A traffic flow model considering influence of car-following and its echo characteristics

Taking into account the driving characteristics of vehicles following the vehicle in front on the imported lane of urban signalized intersections, we introduce the acceleration parameters of the vehicle and consider the queue length and volatility of the acceleration that have been affected by the time of fixed signal cycles in the mixed traffic flow. Thereby, we obtain a mixed traffic flow cellular automaton model with the effect of acceleration on the imported lane. Through analyzing the results of numerical simulation, it is found that the maximum queue length and the volatility of acceleration have a great influence on the intersection lane mixed traffic flow with the different time of fixed signal cycles and considerably on traffic arriving strength within a certain range. When the intensity is in specific range, the longer the fixed signal cycle, the shorter the maximum queue length, and the greater the volatility of acceleration, which has smaller queue jam affecting the intersection lane mixed traffic flow. Meanwhile, the improved model can reproduce the evolution and propagation characteristics of gathering–dissipating of the traffic wave in the intersection lane mixed traffic flow.     

A new simple method of implicit time integration for dynamic problems of engineering structures

This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditional and unconditional stability regions of the parameters. When the control parameters in the method are optimally taken in their regions, the accuracy may be improved to reach of order three. It is found that the new scheme can achieve lower numerical amplitude dissipation and period dispersion than some of the existing methods, e.g. the Newmark method and Zhai’s approach, when the same time step size is used. The region of time step dependent on the parameters in the new scheme is explicitly obtained. Finally, some examples of dynamic problems are given to show the accuracy and efficiency of the proposed scheme applied in dynamic systems. The project supported by the National Key Basic Research and Development Foundation of the Ministry of Science and Technology of China (G2000048702, 2003CB716707), the National Science Fund for Distinguished Young Scholars (10025208), the National Natural Science Foundation of China (Key Program) (10532040), the Research Fund for Oversea Chinese (10228028). The English text was polished by Keren Wang.     

TDGL and mKdV equations for car-following model considering driver’s anticipation

Car-following models are proposed to describe the jamming transition in traffic flow on a highway. In this paper, a new car-following model considering the driver’s forecast effect is investigated to describe the traffic jam. The nature of the model is studied using linear and nonlinear analysis method. A thermodynamic theory is formulated to describe the phase transition and critical phenomenon in traffic flow and the time-dependent Ginzburg–Landau (TDGL) equation is derived to describe the traffic flow near the critical point. It is also shown that the modified Korteweg-de Veris (mKdV) equation is derived to describe the traffic jam. The connection between the TDGL and the mKdV equations is given.     

An extended delayed feedback control method for the two-lane traffic flow

This study extended a delayed feedback control method for the two-lane car-following model. In order to suppress the traffic jams more actually in the two-lane vehicle groups with lane-changing behavior, we introduced the delayed time of receiving the longitudinal and lateral interaction information in the controller into the feedback signals for the control scheme. The stability conditions for different cases were derived, respectively, according to the delayed time by the theory analysis. And the delayed time in the controller was found to instigate the traffic oscillations when the feedback gains were designed improper, which showed that the longer delayed time induces worse traffic jams. The numerical simulation results were found consistent with the theoretical findings as well. Finally, we further presented a comparative study of the proposed control method by a comparison with one existing controller which did not consider the delayed time. And it showed that the delayed time in the controller also affects the traffic flow and performance of control method.