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 can＇ied out and some nonequilibrium phenomena are observed, such as small disturbance instability, stop-and-go waves, local clusters and phase transition.

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.

Extended speed gradient model for traffic flow on two-lane freeways

In this paper, the speed gradient （SG） model is extended to describe the traffic flow on two-lane freeways. Terms related to lane change are added into the continuity equations and velocity dynamic equations. The empirically observed two-lane phenomena, such as lane usage inversion and lane change rate versus density, are reproduced by extended SG model. The local cluster effect is also investigated by numerical simulations.

Analysis of the wave properties of a new two-lane continuum model with the coupling effect

A multilane extension of the single-lane anisotropic continuum model （GK model） developed by Gupta and Katiyar for traffic flow is discussed with the consideration of the coupling effect between the vehicles of different lanes in the instantaneous traffic situation and the lane-changing effect. The conditions for securing the linear stability of the new model are presented. The shock and the rarefaction waves, the local cluster effect and the phase transition are investigated through simulation experiments with the new model and are found to be consistent with the diverse nonlinear dynamical phenomena observed in a real traffic flow. The analysis also focuses on empirically observed two- lane phenomena, such as lane usage inversion and the density dependence of the number of lane changes. It is shown that single-lane dynamics can be extended to multilane cases without changing the basic properties of the single-lane model. The results show that the new multilane model is capable of explaining some particular traffic phenomena and is in accordance with real traffic flow.

Micro-simulation model of two-lane freeway vehicles for obtaining traffic flow characteristics including safety condition

Unidirectional two-lane freeway is a typical and the simplest form of freeway. The traffic flow char- acteristics including safety condition on two-lane freeway is of great significance in planning, design, and manage- ment of a freeway. Many previous traffic flow models are able to figure out flow characteristics such as speed, den- sity, delay, and so forth. These models, however, have great difficulty in reflecting safety condition of vehicles. Besides, for the cellular automation, one of the most widely used microscopic traffic simulation models, its discreteness in both time and space can possibly cause inaccuracy or big errors in simulation results. In this paper, a micro-simula- tion model of two-lane freeway vehicles is proposed to evaluate characteristics of traffic flow, including safety condition. The model is also discrete in time but continu- ous in space, and it divides drivers into several groups on the basis of their preferences for overtaking, which makes the simulation more aligned with real situations. Partial test is conducted in this study and results of delay, speed, volume, and density indicate the preliminary validity of our model, based on which the proposed safety coefficient evaluates safety condition under different flow levels. It is found that the results of this evaluation coincide with daily experience of drivers, providing ground for effectiveness of the safety coefficient.

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

In this paper, the viscous continuum traffic flow model for a single lane is extended to the traffic flow for two-lane freeways. The proposed model is a higher-order continuum model considering the coupling and lane changing effects of the vehicles on two adjacent lanes. It results from integrating the Taylor series expansion of the viscous continuum traffic flow model proposed by Ge （2006 Physiea A 371 667） into the multi-lane model presented by Daganzo （1997 Transpn. Res. B 31 83）. Our proposed model may be used to describe non-anisotropic behaviour because of lane changing in multi-lane traffic. A linear stability analysis is given and the neutral stability condition is obtained. Also, issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are investigated through a simulation experiment. The simulation results show that the proposed model is capable of explaining some particular traffic phenomena commonly observable in real world traffic flow.

Continuum modeling for two-lane traffic flow with consideration of the traffic interruption probability

Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour, this paper establishes a new two-lane microscopic car-following model. Based on this microscopic model, a new macroscopic model was deduced by the relevance relation of microscopic and macroscopic scale parameters for the two-lane traffic flow. Terms related to lane change are added into the continuity equations and velocity dynamic equations to investigate the lane change rate. Numerical results verify that the proposed model can be efficiently used to reflect the effect of the probability of traffic interruption on the shock, rarefaction wave and lane change behaviour on two-lane freeways. The model has also been applied in reproducing some complex traffic phenomena caused by traffic accident interruption.

Controlling traffic jams on a two-lane road using delayed-feedback signals

This paper focuses mainly on the stability analysis of two-lane traffic flow with lateral friction,which may be caused by irregular driving behavior or poorly visible road markings,and also attempts to reveal the formation mechanism of traffic jams.Firstly,a two-lane optimal velocity(OV) model without control signals is proposed and its stability condition is obtained from the viewpoint of control theory.Then delayed-feedback control signals composed of distance headway information from both lanes are added to each vehicle and a vehicular control system is designed to suppress the traffic jams.Lane change behaviors are also incorporated into the two-lane OV model and the corresponding information about distance headway and feedback signals is revised.Finally,the results of numerical experiments are shown to verify that when the stability condition is not met,the position disturbances and resulting lane change behaviors do indeed deteriorate traffic performance and cause serious traffic jams.However,once the proper delayed-feedback control signals are implemented,the traffic jams can be suppressed efficiently.

面向量产的高速公路智能换道系统决策规划方法研究

高速公路智能换道是高级辅助驾驶系统(ADAS)的重要功能,现阶段算法难以在低算力硬件资源条件下兼顾换道安全性和平顺性。为解决此问题,本文提出一种高速公路智能换道系统决策规划方法。通过分级危险区域,检测碰撞风险做出换道决策,进而实施横纵向解耦规划。在横向规划中,设计两阶段五次多项式换道轨迹规划,提升换道途中安全性和平顺性。在纵向规划中,巡航工况采用类PID算法,可提升规划实时性,而跟车工况采用基于同步预测时域的模型预测控制(MPC)算法,通过关联横纵向规划时间可提升换道平顺性,并设计代价函数降低求解复杂度可满足低资源占用要求。通过实车对比试验,验证了该方法在高速公路换道多场景中具有较高的安全性、平顺性和体验感。此外,算法占用的静态区存储和栈区峰值存储测试对比结果表明了该方法具有较低的硬件资源占用率,可满足低算力控制器对资源占用的要求。

变参数两跨四车道桥梁结构设计与分析

为探究两跨四车道桥梁在受到大型船舶撞击时的受力性能,结合第十六届全国大学生结构设计竞赛广东省分区赛赛题《撞击荷载下变参数两跨四车道桥梁结构设计与制作》要求,通过Midas Civil对承受移动荷载和撞击荷载的桥梁结构模型进行数值模拟计算与结构优化设计,最后通过加载试验对仿真计算结果进行验证。研究表明模型节点受力集中且制作复杂,桥梁三级加载时极易出现节点脱落与变形过大导致弦被压断,利用浸润胶水后的竹粉包裹或竹皮缠绕节点可起到较好的加强作用;将主要受力杆件截面设计成T字形,可增加杆件间的接触面积,有效防止加载车道不同引发桥梁偏载时的节点脱落问题。

基于元胞自动机的路内停车对路段通行能力的影响研究

设置路内泊位是解决停车供需不平衡问题的1种重要的措施。然而,不合理的路内泊位设置不仅无法解决停车难的问题,还会降低道路通行能力,导致交通拥堵,从而衍生出一系列交通问题。为进一步从微观层面探究路内停车泊位供求关系以及停车便利性对路段通行能力的影响,构建了1个包括跟驰模型、换道模型和停靠模型的单向双车道元胞自动机模型。在跟驰模型中,通过为停车路段和非停车路段设置不同的慢化概率,探究机动车正常行驶和巡游停靠过程的差异性。在停靠模型中,通过设置停车机动持续时间,解析路内停车便利性对路段通行能力的影响。基于实地调查数据,对模型中正常行驶车辆和巡游停靠车辆的运行规则分别进行了标定,并对模型的可靠性进行了验证。与现有模型的对比分析结果表明,本文模型具有最好的拟合效果,平均绝对误差指标可以降低53.74%~75.71%,能更真实地反应路内停车过程对路段交通流的影响。随着交通流密度的增加,本文模型的平均绝对误差指标可以降低16.39%~52.85%,可以避免过高估计路内泊位对路段通行能力的负面影响,是现有研究的重要补充。在开放边界条件下,分别探究了停车需求、便利性和供给能力变化情景下路段通行能力的变化特征。3种不同场景下路段通行能力均有明显的波动,且停车需求变化的影响最显著。具体地,停车需求由路段交通流量的10%上升至30%时,通行能力下降44.12%;当停车便利性降低,停车机动持续时间由5 s提高到15 s时,通行能力下降24.44%;在500 m的路段上,当停车供给能力由20个停车泊位提高到50个时,通行能力下降39.39%。

地铁列车荷载下类矩形隧道结构动力响应分析

为分析地铁列车荷载作用下类矩形隧道结构的动力响应特性,以郑州地铁8号线郑州东站类矩形盾构段为研究背景,使用MIDAS/GTS NX软件建立三维有限元分析模型,对单车运行与双车交会运行两种工况下类矩形隧道结构的动力响应进行计算分析,得到了类矩形隧道在地铁列车荷载作用下的动力响应规律。结果表明:地铁列车作用下产生的类矩形隧道结构的位移响应和应力响应均较小,隧道结构在地铁列车荷载的作用下是稳定的。地铁列车交会时最大位移发生在衬砌底部,为1.28 mm;在单车运行时,最大位移发生在衬砌行车侧右边,约为0.89 mm。在双车相向行驶时,隧道衬砌左侧的竖向应力响应大于隧道衬砌右侧,其增幅约为26.8%。因此,在地铁运营时期应多对隧道结构左侧行车线下方进行长期的变形监测,以避免在此处发生结构安全问题。

严重冲突场景下山区双车道公路货车跟驰风险预测

为预测严重冲突场景下山区双车道公路货车跟驰事故风险,基于视频轨迹数据、实测交通流数据、道路线形数据及交通事故数据,采用双变量冲突极值模型、轻量型梯度提升机,构建严重冲突场景下山区双车道公路货车跟驰事故风险实时预测(Truck Following Accident Risk Real-Time Prediction,TFARRP)模型,并利用耦合度模型分析变量耦合程度。研究显示:碰撞时间(Time to Collision)为5.418 s,后侵入时间(Post Encroachment Time)为0.512 s,这是严重冲突场景阈值;TFARRP模型准确率高达95.000%;平均车头时距(AHD)、两车间距(TCD)、货车平均速度(TAS)、及货车横向偏移(TLO)对TFARRP模型的重要度都超过了10%;当监测到AHD<21.11 s、TCD<35.00 m、TAS<29.00 km/h或TLO>0.25 m时,应及时发出预警信号,以保证车辆安全行驶。结合4个变量的耦合状况,研究结果可用于双车道公路货车跟驰的短临动态预警系统设计。

双向两车道公路自主超车轨迹规划及跟踪控制

研究了自主地面车辆在双向两车道公路场景下的超车轨迹规划和跟踪控制。建立了权衡换道稳定性和效率的目标函数,得到最优五次多项式换道轨迹。将超车过程分为换道、超越和并道3个阶段,根据超车车辆与其他车辆的临界碰撞条件建立安全距离模型,进而判断超车的可行性,得到超越阶段时长以及规划完整的超车轨迹。分别设计模型预测控制器和离散滑模控制器跟踪横向路径和纵向速度,并利用模糊控制对模型预测控制器输出的前轮转角进行补偿。在Matlab和CarSim联合仿真环境下进行超车验证,结果表明:所提出的超车轨迹规划及跟踪方法能够使车辆实现自主超车机动,并保持良好的跟踪精度和稳定性。

基于EAHP模型的市政隧道原位二扩四爆破效果评价

为准确评判隧道拆除爆破效果,保证原位二扩四市政隧道工程在爆破施工期间车辆正常通行,减少既有隧道衬砌结构爆破拆除及扩挖过程的风险,应用物元理论建立了基于EAHP的隧道爆破效果综合评价模型。首先,从爆破方案设计、爆区周边环境、爆破施工质量、爆破器材及爆破安全技术5个方面选取了29个评价因素指标,并划分为5个评价等级。其次,利用可拓变换构建初等关联函数,计算各爆破效果影响因素指标相对评价等级之间的关联度,同时引入层次分析法(AHP法)确定指标权重,根据最大关联度原则判定隧道爆破效果等级,由此建立基于可拓学-层次分析法的综合评价方法,即EAHP。结果表明,将该方法应用于浙江省楼山隧道原位二扩四工程爆破效果评价,得出爆破效果评定结果为K_(max)=K_(2)=-0.0309,即原位二扩四隧道爆破效果评价级别为“爆破效果较好”,与工程实际情况相吻合。因此,基于EAHP综合评价模型选取的评价指标和权重系数合理可靠,通过可拓变换求得的最大关联度也能较好地反映隧道爆破效果等级,说明基于EAHP模型的综合评价方法对隧道爆破效果评判具有较好的适应性。

超小净距盾构隧道施工对既有隧道变形分析

近年随着我国双线地铁建设快速发展过程中,由于周围的地质情况和城市管线、建筑基础的布局等原因,常常会导致双线隧道间距过小。双线盾构开挖过程中两边隧道难免会产生相互影响。因此,研究双线近距盾构隧道开挖对邻近隧道内力和变形的影响,具有非常重要的实际意义。根据雄安新区至北京大兴国际机场快线工程金融岛站—第五组团站盾构区间工程实例,使用ABAQUS进行建模,模拟超小净距盾构开挖过程中双线隧道的位移变形。研究结果表明:在竖直方向,隧道位移分布均匀,隧道下部部分位移较大;横向位移隧道两端较小,中部较大,根据变形情况讨论该工程过程中可能产生的影响安全性的问题及应对措施。

双车道公路交通安全设计与事故预防

随着社会经济的发展,道路车流量日益增加,在双车道公路交通场景中,可能由于超车驾驶行为而诱发交通事故,为保障行车安全,需要加强对此类公路的交通安全设计。鉴于此,文章提出双车道公路超车安全性不足的问题,再着重围绕其安全设计措施展开探讨,体现在视距、公路线形等方面,阐述一些安全设计措施,以期通过此类措施的落实来有效预防交通事故。

基于改进鱼群算法的双向式立体库货位优化研究

针对现代数字化大型工业立体仓库单一仓位货物数量不定、出入库次数频繁等特点,且多条较长巷道导致的存储效率较低等问题,提出了基于多巷道双向式货物出入库策略,开展货位优化工作。以提高出入库效率、平衡各巷道工作量为目标建立系统货位优化模型,提出了基于平均距离视野的自适应改进人工鱼群算法对该系统进行优化,通过引入视步系数,减少传统鱼群算法对初始参数值的依赖,提高了收敛速度以及收敛值精度。实验结果表明优化效果显著,为现代企业打造基于数字化平台的大型立体库提供了思路,具有重大的研究和实践意义。

基于双车驾驶模拟的城市快速路驾驶人换道交互行为特征

为研究换道情境下换道车辆与目标车道后方车辆驾驶人间的交互行为,设计了城市快速路换道场景,搭建出双车驾驶模拟实验平台,招募40名驾驶人,开展了8种换道场景下的双车实验并进行驾驶风格问卷调查.基于换道阶段实验数据,分析对比了单、双车实验中两车驾驶人的交互行为特征和差异.利用多元Logistic回归模型,分析不同因素对换道交互决策的影响.结果表明:单、双车实验中,换道车辆和目标车道后方车辆的行为特征具有明显差异,从而验证了开展双车实验的必要性;不同的道路限速、换道方向、驾驶风格等因素下,两车驾驶人关键行为变量呈现差异性;道路限速、车辆初始速度、两车纵向位置差、横/纵速度差、纵向速度乘积等均对两车换道交互决策产生显著影响.

考虑车辆运行特性的双车道超车模型

鉴于现有的超车模型往往会忽视超车过程中车辆运行特性对超车行为的影响,文中在现有超车模型的基础上,对超车车辆依据车辆运行特性进行分类,设计了双车道车辆超车场景,并考虑不同道路等级的设计时速,建立了计算超车车辆从超车行为产生到超车过程结束所需的超车时间和距离的数学模型.最后,选择不同类型车辆、超车速度及行车速度,分别计算了微型车、小客车和中大型车在双车道公路超车的时间和距离,并与现有的超车模型计算结果进行对比分析.结果表明:双车道公路超车时间和距离与车辆类型、超车速度、超车车辆与被超车辆的行车速度和对向车辆速度密切相关;文中模型由于考虑车辆的运行特性,不同车辆超车所需的超车时间和距离是不相同的,计算结果更符合实际超车现象.