From rectangle to parallelogram:an area-weighted method to make time-space diagrams incorporate traffic waves

A time-space(TS)traffic diagram is one of the most important tools for traffic visualization and analysis.Recently,it has been empirically shown that using parallelogram cells to construct a TS diagram outperforms using rectangular cells due to its incorporation of traffic wave speed.However,it is not realistic to immediately change the fundamental method of TS diagram construction that has been well embedded in various systems.To quickly make the existing TS diagram incorporate traffic wave speed and exhibit more realistic traffic patterns,the paper proposes an area-weighted transformation method that directly transforms rectangular-cell-based TS(rTS)diagrams into parallelogram-cell-based TS(pTS)diagrams,avoiding tracing back the raw data of speed to make the transformation.Two five-hour trajectory datasets from Japanese highway segments are used to demonstrate the effectiveness of the proposed methods.The travel time-based comparison involves assessing the disparities between actual travel times and those computed using rTS diagrams,as well as travel times derived directly from pTS diagrams based on rTS diagrams.The results show that travel times calculated from pTS diagrams converted from rTS diagrams are closer to the actual values,especially in congested conditions,demonstrating superior performance in parallelogram representation.The proposed transformation method has promising prospects for practical applications,making the widely-existing TS diagrams show more realistic traffic patterns.

DESCRIPTION AND WENO NUMERICAL APPROXIMATION TO NONLINEAR WAVES OF A MULTI-CLASS TRAFFIC FLOW LWR MODEL

A strict proof of the hyperbolicity of the multi-class LWR ( Lighthill-Whitham-Richards) traffic flow model, as well as the descriptions on those nonlinear waves characterized in the traffic flow problems were given. They were mainly about the monotonicity of densities across shocks and in rarefactions. As the system had no characteristic decomposition explicitly, a high resolution and higher order accuracy WENO( weighted essentially non-oscillatory) scheme was introduced to the numerical simulation, which coincides with the analytical description.

Density waves in a lattice hydrodynamic traffic flow model with the anticipation effect

By introducing the traffic anticipation effect in the real world into the original lattice hydrodynamic model, we present a new anticipation effect lattice hydrodynamic （AELH） model, and obtain the linear stability condition of the model by applying the linear stability theory. Through nonlinear analysis, we derive the Burgers equation and Korteweg-de Vries （KdV） equation, to describe the propagating behaviour of traffic density waves in the stable and the metastable regions, respectively. The good agreement between simulation results and analytical results shows that the stability of traffic flow can be enhanced when the anticipation effect is considered.

Solitary wave solution to Aw-Rascle viscous model of traffic flow

A traveling wave solution to the Aw-Rascle traffic flow model that includes the relaxation and diffusion terms is investigated. The model can be approximated by the well-known Kortweg-de Vries （KdV） equation. A numerical simulation is conducted by the first-order accurate Lax-Friedrichs scheme, which is known for its ability to capture the entropy solution to hyperbolic conservation laws. Periodic boundary conditions are applied to simulate a lengthy propagation, where the profile of the derived KdV solution is taken as the initial condition to observe the change of the profile. The simulation shows good agreement between the approximated KdV solution and the numerical solution.

KINEMATIC WAVE PROPERTIES OF ANISOTROPIC DYNAMICS MODEL FOR TRAFFIC FLOW

The analyses of kinematic wave properties of a new dynamics model for traffic flow are carried out. The model does not exhibit the problem that one characteristic speed is always greater than macroscopic traffic speed, and therefore satisfies the requirement that traffic flow is anisotropic. Linear stability analysis shows that the model is stable under certain condition and the condition is obtained. The analyses also indicate that the model has a hierarchy of first- and second-order waves and allows the existence of both smooth traveling wave and shock wave. However, the model has a distinctive criterion of shock wave compared with other dynamics models, and the distinction makes the model more realistic in dealing with some traffic problems such as wrong-way travel analysis.

A NOTE ON THE INTERACTIONS OF ELEMENTARY WAVES FOR THE AR TRAFFIC FLOW MODEL WITHOUT VACUUM

In this note, we consider the interactions of elementary waves for the traffic flow model proposed by Aw and Rascle when the vacuum is not involved. The solutions are obtained constructively and globally when the initial data consist of three pieces of constant states. Furthermore, it can be found that the Riemann solutions are stable with respect to such small perturbations of the initial data in this particular situation by investigating the limits of the solutions as the perturbed parameter ε goes to zero.

Green-Wave Traffic Theory Optimization and Analysis

This paper analyzed the applicable conditions of the Green-Wave traffic theory, used two-phase signal control concept to optimize the Green-Wave traffic theory, put forward specific program for cross intersections and T-intersections. The analysis concluded that the optimized Green-Wave traffic theory is favorable to improve road safety and reduce vehicle fuel consumption and reduce vehicle emissions and other aspects.

Travel time function for basic link considering signal control in network traffic model

In order to describe the travel time of signalcontrolled roads, a travel time model for urban basic roads based on the cumulative curve is proposed. First, the traffic wave method is used to analyze the formation and dispersion of the vehicle queue. Cumulative curves for road entrances and exits are established. Based on the cumulative curves, the travel time of the one-lane road under stable flow input is derived. And then, the multi-lane road is decomposed into a series of single-lane links based on its topological characteristics. Hence, the travel time function for the basic road is obtained. The travel time is a function of road length, flow and control parameters. Numerical analyses show that the travel time depends on the supply-demand condition, and it has high sensitivity during peak hours.

On the critical conditions of traffic jams

Traffic wave theory is used to study the critical conditions for traffic jams according to their features. First, the characteristics of traffic wave propagation is analyzed for the simple signal-controlled lane and the critical conditions for oversaturation is established. Then, the basic road is decomposed into a series of one-way links according to its topological characteristics. Based on the decomposition, traffic wave propagation under complex conditions is studied. Three complicated factors are considered to establish the corresponding critical conditions of jam formation, namely, dynamic and insufficient split, channelized section spillover and endogenous traffic flow. The results show that road geometric features, traffic demand structures and signal settings influence the formation and propagation of traffic congestion. These findings can serve as a theoretical basis for future network jam control.

智能网联环境下信号交叉口车辆轨迹重构模型

车辆轨迹数据提供了大量的时空交通流信息,可用于各类交通研究.传统车辆轨迹模型多以人工驾驶环境为研究对象,普遍未考虑由常规车(RV)、网联人工驾驶车(CV)以及智能网联车(CAV)组成的混合交通流的影响.为解决该问题,构建智能网联环境下信号交叉口全样本车辆轨迹重构模型.首先,介绍并分析智能网联环境下城市道路交叉口处车辆组成及排队通过情况;然后,构建城市道路混合交通流轨迹数量估计模型,并针对前后车的排队情况提出虚拟车的概念,用于估计不同车辆的交通状态;最后,设计数值仿真实验分析交通流密度和网联车渗透率对模型的影响,并基于NGSIM数据进行实例验证.结果表明:轨迹重构模型的数量误差和位置误差均随着交通流密度和网联车渗透率的增大而减小,如交通流密度由20 veh/km增大至50 veh/km的过程中,模型数量误差和位置误差均呈现下降趋势,且最大误差分别不超过6.88%和8.02 m;与网联人工驾驶车渗透率相比,智能网联车的渗透率对模型结果影响更大.

小型音乐厅减振隔声改造实践

为解决邻近交通线路带来的振动与噪声干扰问题,采用“房中房”方案,对首都师范大学音乐厅开展减振隔声改造工程。在改造实践中,克服构造改动限制多、减振隔声难度大等难点,系统地采用浮筑地面、隔声墙、减振吊顶、隔音门窗等全方位的隔声与减振改进措施。改造后经过测量,音乐厅的室内声环境已符合相关标准要求,预期目标得以实现。所提出的减振隔声措施可为类似体量中小型音乐厅的改造实践提供参考。

超高速公路三波护栏安全性影响因素仿真分析

文中基于利用HeperWorks和LS-DYNA软件进行碰撞仿真,对三波护栏进行单影响因素和多影响因素分析.结果表明:波形梁厚度5 mm时,三波护栏防护性较好,立柱间距2000 mm时,护栏最大动态变形量减小,汽车合成加速度峰值超出20 g安全值,不能保证乘员安全.护栏最大动态变形量和绊阻与碰撞速度、碰撞角度、立柱间距成正比,与波形梁厚度成反比,汽车合成加速度与碰撞速度、碰撞角度成正比,与波形梁厚度和立柱间距成反比.

考虑路径关系的干线多路径绿波优化模型

针对协调路径数目增加后绿波带宽变窄问题,本文提出一种考虑路径关系的多路径协调控制优化模型。分析路径的相关关系,构建上下行分区和路径分解模型;引入子区划分参数,改进经典多路径模型,构建子区内部协调约束;分析路径在相邻子区之间的衔接特征,构建子区间连接性约束条件;综合考虑子路径长度和流量构建权重系数,以各子路径绿波带宽加权和最大为优化目标,建立多路径协调控制优化模型。为验证模型的有效性,选取南京市典型干道为研究对象开展案例分析。实验结果表明,本文提出的模型可以有效增大绿波带宽,相较于对比模型,加权绿波带宽和提高49.44%。利用VISSIM验证了方案的应用效果,仿真结果表明,本文模型方案可以获得更高的通行效益。相较于对比方案,关键路径车均延误和车均停车次数明显降低,干道车均延误和车均停车次数分别降低了20%和27%,车辆平均速度提高了17%。本文模型可为城市道路干线协调控制提供理论基础。

高铁箱梁桥顶板纵向加筋对其声振特性的影响

伴随着高速铁路箱梁桥的大规模建设,列车经过时引起的高架桥低频声辐射问题已成为限制其发展重要因素之一。为了缓解列车经过箱梁桥时的声辐射问题,有必要开展桥梁降噪措施研究。以高速铁路箱梁桥为研究对象,对箱梁桥顶板增设纵向筋板,采用多体系统动力学软件UM及有限元-边界元方法建立车辆-轨道-桥梁耦合动力学模型和声学预测模型,对原结构箱梁桥和加筋板箱梁桥的振动加速度、辐射声功率、线性声压级和声场分布等进行分析,研究顶板纵向加筋对箱梁桥声振特性的影响。研究结果表明:增设纵向筋板后箱梁桥各个板件振动加速度都明显减小,在顶板处减幅最大;增设纵向筋板后箱梁桥的辐射声功率和声压级明显降低,降噪效果良好;其对桥上声场的降噪效果好于桥下和桥侧声场。

基于决策树模型的管制员工作负荷检测

为了验证gamma波是否更适用于管制员工作负荷检测,首先设计预实验选取代表性强、区分度大的管制场景场景,在此基础上,设计实验获取管制员在不同工作场景下的脑电(electroencephalogram,EEG)数据及工作负荷数据,并通过S-W(Shapiro-Wilk)检验验证了选取的实验场景的有效性。随后,提出一系列脑电特征并对根据实际情况对脑电数据划分方法做出改进,并对脑电特与工作负荷的相关性进行分析。结果表明:与gamma波相关的特征β+θ+α+γ与工作负荷的相关性最高,可用于管制员的工作负荷检测。最后,选用“留一交叉验证法”建立决策树回归模型对管制员的工作负荷进行检测。检测精度可达0.979~0.996,证明与gamma波相关的功率谱特征可用于管制员工作负荷的检测。

基于衔接交叉口绿波交通的快速路入口匝道信号控制策略

基于快速路入口匝道与衔接交叉口的绿波交通构建了快速路入口匝道信号控制模型。通过合肥市裕溪路高架对智能控制方案进行算法验证,结果表明:智能控制方案在晚高峰时间段,提升了快速路服务水平,快速路主线行程时间降低率保持在20%以上,在晚高峰时期交通流量提升率在40%以上,主线速度提升30%以上。

智能网联测试场混合交通流仿真研究

智能网联汽车的出现为解决交通问题提供了新的技术手段。通过智能网联汽车与交通控制协同策略消除交通冲击波的生成和传播影响是提高交通效率与安全的有效手段之一。研究对混合流下的智能网联车辆速度控制与可变限速控制以及两者的协同控制模型与机制,通过搭建测试场数字孪生感知平台,获取测试场高环区域内的实时混合交通流数据,并构建协同控制模型框架与最优化求解办法,探究协同管控策略在测试场高环场景下对交通效率与安全的实际效果。通过仿真实验,对比交通效率、安全等核心指标,显示的协同控制策略对测试场交通流碰撞时间分布数据优化了50%以上,对当前场景的总行程时间优化超过20%,为智能网联车辆控制优化交通流提供解决思路。

近红外物联网节点失效波影响分析模型构建

近红外物联网节点失效波对网络连接可靠率具有重要影响,为提升近红外物联网安全防范力度,构建基于链路生存性流量的节点失效波影响分析模型。构建近红外物联网节点行为信任轮廓,加权求和主观信任值、客观推荐信任值和过往信任值,得到节点行为综合信任值,评估节点是否产生异常;利用节点重要度与负载能力实施失效负载再分配,组建节点失效传播模型,计算随机相邻节点额外业务负载,若高于自身负载能力则节点存在失效风险;根据链路持续时长和剩余容量推导链路生存性,计算相邻节点的引入流量和失效波影响概率,划分节点失效波影响等级,获得近红外物联网不同时段节点失效波影响情况。实验结果表明,所构建模型能准确描述近红外物联网处于不同外部环境下的节点失效波影响程度,为近红外物联网稳定运行提供借鉴。

Speed–density functional relationship for heterogeneous traffic data: a statistical and theoretical investigation

This study is an attempt to establish a suitable speed–density functional relationship for heterogeneous traffic on urban arterials. The model must reproduce the traffic behaviour on traffic stream and satisfy all static and dynamic properties of speed–flow–density relationships. As a first attempt for Indian traffic condition, two behavioural parameters, namely the kinematic wave speed at jam(Cj) and a proposed saturation flow(k), are estimated using empirical observations. The parameter Cjis estimated by developing a relationship between driver reaction time and vehicle position in the queue at the signalised intersection. Functional parameters are estimated using Levenberg–Marquardt algorithm implemented in the R statistical software.Numerical measures such as root mean squared error, average relative error and cumulative residual plots are used for assessing models fitness. We set out several static and dynamic properties of the flow–speed–density relationships to evaluate the models, and these properties equally hold good for both homogenous and heterogeneous traffic states.From the numerical analysis, it is found that very few models replicate empirical speed–density data traffic behaviour.However, none of the existing functional forms satisfy all the properties. To overcome the shortcomings, we proposed two new speed–density functional forms. The uniqueness of these models is that they satisfy both numerical accuracy and the properties of fundamental diagram. These new forms would certainly improve the modelling accuracy, especially in dynamic traffic studies when coupling with dynamic speed equations.

基于毫米波雷达的高速公路全天候超视距车流量监测研究

随着城市化的加速、高速公路的普及和汽车数量的增加,高效的交通流量监测系统变得尤为关键。传统方法如地感线圈和视觉系统虽应用广泛,但其依赖于视线和良好的光照条件,限制了它们在复杂环境中的效能。毫米波雷达技术以其高频率的特性提供了较高的分辨率和穿透能力,适合在各种气候和光照条件下工作。文中介绍了一种基于毫米波雷达的高速公路全天候超视距车流量监测系统,该系统能有效提升交通管理的效率与安全性,并通过实例展示了其在实际应用中的成效和好处。