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.

Minimum Time Overtaking Problem of Vehicle Handling Inverse Dynamics Based on Two Kinds of Safe Distances

Overtaking accidents caused by improper operations performed by a driver occur frequently. However, most stud?ies on overtaking safety have neglected research into driver control input. A novel method is proposed to obtain the driver control input during the overtaking process. Meanwhile, to improve the safety of overtaking, two types of safe distances, and the time of the overtaking are considered. Path constraints are established when considering the two types of safe distances. An optimal control model is established to solve the minimum time maneuver under multiple constraints. Using the Gauss pseudospectral method, the optimal control problem is converted into a nonlinear pro?gramming problem, which is then solved through sequential quadratic programming(SQP). In addition, the e ective?ness of the proposed method is verified based on the results of a Carsim simulation. The simulation results show that by adopting an inverse dynamics method to solve the manipulation problem of the vehicle’s minimum overtaking time, the manipulation capability of a vehicle in completing an overtaking safely within the minimum time can be obtained. This method can provide a reference for research into the active safety of manned and unmanned vehicles.

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.

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.

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.

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.

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.

基于驾驶模拟的超车仿真教学实验设计

道路交通运输专业具有多学科融合、紧密结合实践的特点,但许多交通专业课程的实践教学环节往往会受到场地大小、条件不可控、重复性差和实际道路危险性等不利因素的限制而无法顺利开展。为提升学生的实践能力与课程参与度,基于驾驶模拟技术,探讨可用于交通仿真、道路交通安全及交通行为分析等课程教学的超车仿真教学实验项目,教学实验以锻炼学生分析解决问题能力和实践操作能力为目标,详细地设计实验流程与实践教学内容,并将该实验项目在道路交通安全、交通仿真等课程的实践环节进行应用,为驾驶模拟系统在教学实验中的应用提供参考。

既有地铁线非站站停列车开行方案与越行站设置协同优化研究

研究既有地铁非站站停列车开行方案和越行站设置协同优化对提高线路通过能力和运输效率具有重要意义。将非站站停列车开行方案编制与越行站设置协同考虑,出行乘客以出行OD分类,构建以企业运营成本、乘客出行成本以及列车越行成本最低为目标的既有地铁线非站站停列车开行方案优化模型,考虑线路通过能力及快车停靠等约束,依据模型特点选用遗传模拟退火算法进行模型求解。以西安地铁14号线为例验证构建模型有效性,求解结果表明:与传统的站站停运营组织模式相比,乘客总在车时间降低29.84%,企业运营成本降低4.33%,车底购置成本降低5.23%,同时讨论不同越行站位置选择对企业运营成本的影响,为轨道公司实施非站站停运营组织模式及相关车站改造提供决策支撑。

后发经济体在全球产业链重构中的弯道超车——历史经验及对中国的启示

全球产业链重构为后发经济体提供了弯道超车的机会,有利于其充分发挥自身的后发优势,实现本土产业链的长足发展。纵观全球产业链发展史,颠覆性的技术创新、比较优势变化和全球治理体系变革是驱动全球产业链重构的主要机制。到目前为止,全球产业链共经历了五次重构,依次伴随着美国、日本、“亚洲四小龙”、中国以及南亚和东南亚地区等相应时期后发经济体的崛起。通过研究驱动机制和后发经济体案例,本文发现后发经济体在参与全球产业链重构时,需重点关注核心技术、需求市场以及国际经贸规则等方面,从而充分发挥后发优势,实现弯道超车。基于此,中国应借鉴后发经济体在全球产业链重构中的弯道超车经验,抓住目前全球产业链重构的新发展机遇,不断推动技术进步以促进产业链升级,不断扩大内需以保障产业链安全,还应积极参与全球治理规则重构,为全球治理体系变革贡献中国方案。

基于多目标优化的高速超车轨迹规划

为保障高速超车规划过程中的安全,同时提升轨迹的舒适性,笔者提出一种基于多目标的高速超车轨迹规划算法。该算法在可行凸空间的基础上求解出高速超车边界条件,再通过安全超车策略对超车行为的可行性进行分析,随后根据建立的超车轨迹规划目标函数和舒适性优化函数对轨迹的平顺性和乘坐的舒适性等目标进行优化,并且算法实时规划轨迹直至超车行为完成。为验证该算法的有效性,利用Prescan和MATLAB/Simulink构建联合仿真平台,对所设计的两种常见超车场景进行验证分析。仿真结果表明:在匀速超车以及加速超车场景下,相较于单目标优化,经多目标优化的超车轨迹的横向位移峰值、横向加速度峰值、横摆角速度峰值、曲率峰值,以及车速峰值的优化效果都获得了提升,有效的提高了所规划超车轨迹的舒适性和安全性。

考虑船间效应和操纵性能的内河船舶追越风险模型及应用

针对内河在航船舶追越过程中碰撞事故频发的问题,构建考虑船间效应和操纵性能的内河船舶追越风险模型。对内河在航船舶追越过程进行情景分析,从纵向和横向距离两个方面综合考虑船舶追越风险。引入船舶纵向安全距离模型和紧急转舵距离,提出不同危险局面下的纵向距离计算方法。考虑船间效应和船舶保向性,根据力和力矩方程,提出不同会遇时刻的横向距离计算方法。构建基于模糊逻辑的内河船舶追越风险模型,选取100组长江典型追越案例验证模型的可行性。

二级公路“2+1”车道布局模式关键设计参数研究

采用“2+1”车道布局有利于解决现状双车道二级公路车辆排队、强行超车等问题,但由于目前国内尚未针对“2+1”车道设计理论开展系统研究,其工程实践非常欠缺。通过对公路设计规范、国外“2+1”车道设计等资料的分析,确定了二级公路“2+1”车道布局概念模式,并运用交通工程与交通安全方法,对“2+1”车道二级公路超车段、合流与分流渐变段长度等关键参数开展了理论分析,然后运用交通仿真手段,采用效率评价指标对理论分析结果进行测试、调优,最终确定了“2+1”车道设计最优参数及适应交通量。其研究成果能为“2+1”车道在我国二级公路上的应用提供技术参考,有望丰富我国二级公路设计建设相关标准。

浮泥层对船船干扰影响的数值计算

针对浮泥层对船船干扰的影响问题,通过求解RANS方程对浮泥水域中追越船与被追越船间的水动力干扰问题进行数值模拟.对比分析了有无浮泥时追越船与被追越船所受力和力矩特点,讨论了在浮泥水域中不同水深吃水比、富裕水深及航速比变化对两船所受力和力矩的影响.结果表明:浮泥层会扩大船船干扰的范围;追越船所受力和力矩及被追越船所受力矩各极值随富裕水深的增大而减小;水深吃水比一定时,追越船所受力和力矩各极值随浮泥厚度的增大而增大;被追越船所受力和力矩各极值随航速比的增大而减小;船尾散波发散角度随船速的增大而减小.

基于DEA模型的动车组列车运行线效率评价

运行线是列车运行图的重要组成元素,运行线效率是反映运行图相对质量的评价指标,从系统的角度分析运行线,其效率可以简化为技术指标与投入运输资源的比值。考虑到中低速列车为待避高速列车会造成自身效率下降,很难用一套标准对各类列车运行线效率进行客观有效的评价。为反映系统与元素、元素与元素之间的相互影响,考虑区间车站的繁忙程度和列车之间的越行成本,构建列车运行线效率计算模型。以某季度列车运行图数据进行实例验证,计算结果中低速列车与高速列车的效率差值明显缩小了,说明不同速度等级列车的效率具备可比性;再对某季度全路列车运行图数据进行实例分析,结果表明采用高速度等级运行标尺列车的综合效率高于全图其他类别列车;最后通过DEA的投影分析,对提高列车运行线效率给出针对性建议。

北京市中心城区外地铁线路开行快慢车对策研究

随着城市化进程的进一步加快,城市居民对通勤出行的时效性要求越来越高,连接中心城与外围新城之间的地铁是主要的通勤交通线路,如何提高其旅行速度、缩短乘客旅行时间,成为急需研究的一个重要问题。为满足不同乘客对出行条件和服务效率的需求,提出通过开行快慢车实现旅速时间的节省。从既有客流特征入手,分析客流来源及目的地,指出既有线开行快慢车的必要性;在借鉴日本相关案例经验的基础上,对开行快慢车需要考虑的问题进行分析;以北京燕房线、房山线、15号线为例,分析不同线路的客流特征及线路条件,分别提出利用大行车间隔及设置越行线开行快慢车的方案;并提出两种方案的特点及实施要点。利用大行车间隔开行快慢车,即在客流较小的线路上利用富裕的能力开行快慢车,仅需对运营图进行优化设计,投资小;设置越行线开行快慢车,需根据工程实施条件、客流特征,选择合理的越行站点。经分析研究,采用两种方式均可实现节省旅行时间的目的,对提升中心城区外客流快速进城需求有积极的意义。

Leveraging Augmented Reality,Semantic-Segmentation,and VANETs for Enhanced Driver’s Safety Assistance

Overtaking is a crucial maneuver in road transportation that requires a clear view of the road ahead.However,limited visibility of ahead vehicles can often make it challenging for drivers to assess the safety of overtaking maneuvers,leading to accidents and fatalities.In this paper,we consider atrous convolution,a powerful tool for explicitly adjusting the field-of-view of a filter as well as controlling the resolution of feature responses generated by Deep Convolutional Neural Networks in the context of semantic image segmentation.This article explores the potential of seeing-through vehicles as a solution to enhance overtaking safety.See-through vehicles leverage advanced technologies such as cameras,sensors,and displays to provide drivers with a real-time view of the vehicle ahead,including the areas hidden from their direct line of sight.To address the problems of safe passing and occlusion by huge vehicles,we designed a see-through vehicle system in this study,we employed a windshield display in the back car together with cameras in both cars.The server within the back car was used to segment the car,and the segmented portion of the car displayed the video from the front car.Our see-through system improves the driver’s field of vision and helps him change lanes,cross a large car that is blocking their view,and safely overtake other vehicles.Our network was trained and tested on the Cityscape dataset using semantic segmentation.This transparent technique will instruct the driver on the concealed traffic situation that the front vehicle has obscured.For our findings,we have achieved 97.1% F1-score.The article also discusses the challenges and opportunities of implementing see-through vehicles in real-world scenarios,including technical,regulatory,and user acceptance factors.

基于城市超车工况的智能车辆避障规划方法研究

在城市道路行驶中,超车驾驶既是常见的驾驶行为,也是常见的交通事故工况之一。基于改进人工势场法(artificial potential field method)与模型预测控制(model predicition control)提出了一种避障规划控制方法。首先,构建目标点引力势场函数、道路及车道线势场函数以及障碍物车辆势场函数;其次,基于势场函数建立统一化模型函数;最后,对系统进行模拟实验评估。结果表明,提出的避障规划控制方法能够生成安全、平滑的路径,其前轮转角变化范围在[−0.67°,1.02°],质心侧偏角变化范围在[−0.22°,0.32°],具有稳定的控制能力。

400 km/h高速铁路通过能力计算方法研究

本文旨在研究全高速模式下基于扣除系数法的400 km/h高速铁路的通过能力计算方法。首先,对不同运行图铺画方式下的扣除系数进行了深入分析,并确定了其计算方法。在群组中列车数量一定的情况下,停站数量较少时按停站列车成组铺画不越行,扣除系数较小;停站数量较多时按成组不停站列车越行停站列车铺画,扣除系数较小。然后,进一步提出了基于扣除系数法的通过能力计算方法,并对影响通过能力的主要因素进行了敏感性分析。结果显示,区间追踪间隔时间的变化对通过能力的影响最为显著。此外,本文还探讨了扣除系数与400 km/h高速铁路列车和线路间的内在联系,并通过构造算例,验证了计算方法的正确性和有效性。这一研究为提高高速铁路的运营效率提供了理论支持和实践指导。