基于运行速度的高速公路直线段最小长度取值研究

文章从车辆的实际运行情况出发,以车辆在直线段上仅经历加速和减速阶段作为直线段最小长度的控制条件,分别推导了平直路段和直坡路段基于运行速度的直线段最小长度计算模型,并以现场实测数据为依据,建立了高速公路平曲线起终点小客车运行速度与平曲线半径的回归模型,并结合某高速公路案例进行了计算分析。结果表明:考虑纵坡的直线段最小长度比平直线段最小长度长;同向曲线间直线段长度能满足不宜小于6倍设计速度的规范要求,但可能不满足所建立模型中车辆运行对最小长度的需求。     

雾环境下山区高速公路车辆运行速度分析

科学地分析雾环境下山区高速公路车辆运行速度变化特征,为改善山区高速公路车辆运行环境,提高山区高速公路的运行安全性具有重要意义。为了能够清晰地描述山区高速公路车辆运行速度的变化规律,本文采用现场试验的方式收集驾驶员在雾环境下对车辆间距及目标物识别距离的判断情况,分析了不同能见度环境下车速的变化规律,研究表明山区高速公路行车过程中,驾驶员受雾环境的影响,能见度越低,驾驶员对车辆间距的估计值越大,对目标物的识别距离越短,平均运行速度越低。     

一种针对长陡坡感应式液压升降减速带组合

减速带作为目前最主要的减速设施,在降低车速减少交通事故发生的同时,仍存在减速不彻底、驾驶员舒适性差等缺点。针对以上问题,提出了主要侧重长陡坡路段的智能升降减速带系统。依据奖“慢”罚“快”的原则,通过对传统减速带结构进行改进,设置不同的高度对应不同速度,再结合雷达测速与液压升降系统,在保证低速驶过车辆平顺性和舒适性的同时,对高速驶过车辆产生更大的颠簸感,迫使其主动减速。通过采集、数据分析、传导到升降的智能化协作,提升减速带对车辆的精准化减速效果。     

基于VISSIM的高速公路隧道交通事故影响仿真分析

为了研究高速公路长大隧道内交通事故影响程度,文章以江西省第一长隧道九岭山隧道为研究对象,通过VISSIM交通仿真软件建立交通仿真模型,在设置不同等级的交通流量以及大货车交通比例的条件下,仿真获得高速公路长大隧道交通事故发生后车辆排队长度以及延误时间,用以分析高速公路隧道内交通事故对隧道通行能力的影响,以更大程度上实现高速公路隧道安全行车。     

高速公路连续长下坡路段行车安全分析

连续长下坡路段是高速公路交通事故的多发路段,而载重汽车又占了肇事车辆的绝大多数.从车辆的运行特征、制动性能、超载行驶等方面分析了目前长下坡路段载重车辆事故多发的原因,并采用刹车毂的实测温度来评价车辆的制动性能,以此作为沿线避险车道、加水站等交通安全设施的设计依据.     

基于元胞自动机的双车道变道交通流特性研究

在庞杂的城市交通环境下,驾驶员为了寻求更快的速度,常常采用主动的换道行为。由于汽车使用量逐年增长,换道引起的交通事故经常发生。研究车辆变道行为,寻求有效措施减少交通事故的发生,对提高道路安全性具有积极的意义。本文以多车道系统中车辆变道行为为研究对象,以元胞自动机理论为基础,对比分析单向单车道、单向双车道换道行为,并运用MATLAB仿真软件进行分析,获得变道交通流的相关特性曲线。     

平头车与长头车谁更安全？

近年来．在多起交通事故中,营运车辆成为交通事故中的主要群体。其中．相当部分交通事故中的人员死因与我国大部分汽车的平头设计有关。这是江西省公安厅交警总队近期组织调研小组,以大型货运车辆为切入点,对平头汽车的安全现状进行了深入调研后的结论。     

考虑危险驾驶群体的交通事故预测模型

传统的交通事故预测是基于直接暴露量,如车辆行驶里程(VMT)等,很少有研究致力于评估不同驾驶群体对事故频率的影响,而现有的研究表明,大量的交通事故与驾驶群体相关。基于此,首先采用相对危险暴露量技术探索所有驾驶人群中的危险驾驶群体,通过相关事故参与率的计算结果可知,青年(15~29岁)和老年(大于或等于70岁)驾驶员更容易发生事故,为危险驾驶群体。然后以VMT和危险驾驶群体作为解释变量,建立了用于交通事故预测的负二项模型。最后通过计算Akaike信息准则(AIC)指标,得到了最优预测模型。结果表明,将危险驾驶群体引入交通事故预测模型可以使预测效果更好(尤其是以VMT和青年驾驶员为变量),有助于提高交通事故预测的准确性。     

基于VISSIM交通仿真的道路安全性评价

随着高速公路的快速发展,车辆数量的逐年递增,交通事故时有发生,不仅造成财产损失,更重要的是造成人员伤亡,因此对于道路安全性评价愈发重要。传统的评价方法计算复杂或是基于已建成的道路,缺乏实际可操作性。本文以西宁至互助一级公路初步设计为依托工程,基于道路运行速度的安全性评价标准,提出了应用VISSIM交通仿真软件的拟建道路线性设计。通过该方法可以进行提前改建与重新设计,避免由于道路线型造成交通事故。所述方法可以为今后拟建道路安全性评价提供了直观有效且科学的方法指导与理论基础。     

运行速度及其在公路路线设计中的应用分析

我国现行的公路路线设计方法以设计速度为核心,但是设计速度与车辆行驶速度严重脱节,公路线形的指标并不能满足运行速度下的安全要求。基于运行速度的概念,文章分析了运行速度的影响因素,对运行速度的获取方法进行了总结,并在上述工作的基础上,介绍了运行速度在公路路线设计工作中的应用,为公路路线设计工作提供参考。     

Evaluating effects of traffic and vehicle characteristics on vehicular emissions near traffic intersections

Urban air quality is generally poor at traffic intersections due to variations in vehicles’ speeds as they approach and leave. This paper examines the effect of traffic, vehicle and road characteristics on vehicular emissions with a view to understand a link between emissions and the most likely influencing and measurable characteristics. It demonstrates the relationships of traffic, vehicle and intersection characteristics with vehicular exhaust emissions and reviews the traffic flow and emission models. Most studies have found that vehicular exhaust emissions near traffic intersections are largely dependent on fleet speed, deceleration speed, queuing time in idle mode with a red signal time, acceleration speed, queue length, traffic-flow rate and ambient conditions. The vehicular composition also affects emissions. These parameters can be quantified and incorporated into the emission models. There is no validated methodology to quantify some non-measurable parameters such as driving behaviour, pedestrian activity, and road conditions     

Appraisal of traffic stream friction

This paper presents a simulation model to evaluate the quality of traffic flow. The evaluation is based on counts of the number of potential speed changes on a stretch of road and the estimated number of times a vehicle is limited in changing lanes. In order to describe the behaviour of the traffic flow process, two models were developed. One model describes vehicle arrival patterns on a road cross section; the other model, vehicle speeds. The stochastic process of speed is described as an autoregression process, whereas vehicle arrivals are presented as a Markovian process. Simulation results indicate an increase in traffic stream friction with an increase in vehicle-speed standard deviation and a reduction in average speed. The dependence of vehicle arrivals in adjacent lanes seems to increase the amount of friction in each lane. The simulation model developed enables a comparison of the quality of traffic flow at different sites, as well as a before-and-after study of any particular site.     

Network-wide traffic and environmental impacts of acceleration and deceleration among Eco-Driving Vehicles in different road configurations

Eco-Driving, a driver behaviour-based method, has featured in a number of national policy documents as part of CO₂ emission reduction or climate change strategies. This investigation comprises a detailed assessment of acceleration and deceleration in Eco-Driving Vehicles at different penetration levels in the vehicle fleet, under varying traffic composition and volume. The impacts of Eco-Driving on network-wide traffic and environmental performance at a number of speed-restricted road networks (30?km/h) is quantified using microsimulation. The results show that increasing levels of Eco-Driving in certain road networks result in significant environmental and traffic congestion detriments at the road network level in the presence of heavy traffic. Increases in CO₂ emissions of up to 18% were found. However, with the addition of vehicle-to-vehicle or vehicle-to-infrastructure communication technology which facilitates dynamic driving control on speed and acceleration/deceleration in vehicles, improvements in CO₂ emissions and traffic congestion are possible using Eco-Driving.     

Analysis of a cooperative variable speed limit system using microscopic traffic simulation

Variable speed limit systems where variable message signs are used to show speed limits adjusted to the prevailing road or traffic conditions are installed on motorways in many countries. The objectives of variable speed limit system installations are often to decrease the number of accidents and to increase traffic efficiency. Currently, there is an interest in exploring the potential of cooperative intelligent transport systems including communication between vehicles and/or vehicles and the infrastructure. In this paper, we study the potential benefits of introducing infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits in variable speed limit systems. We do this by proposing a cooperative variable speed limit system as an extension of an existing variable speed limit system. In the proposed system, communication between the infrastructure and the vehicles is used to transmit variable speed limits to upstream vehicles before the variable message signs become visible to the drivers. The system is evaluated by the means of microscopic traffic simulation. Traffic efficiency and environmental effects are considered in the analysis. The results of the study show benefits of the infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits for variable speed limit systems in the form of lower acceleration rates and thereby harmonized traffic flow and reduced exhaust emissions.     

Heterogeneous traffic flow modelling for an arterial using grid based approach

A grid based modelling approach akin to cellular automata (CA) is adopted for heterogeneous traffic flow simulation. The road space is divided into a grid of equally sized cells. Moreover, each vehicle type occupies one or more cell as per its size unlike CA traffic flow model where each vehicle is represented by a single cell. Model needs inputs such as vehicle size, its maximum speed, acceleration, deceleration, probability constants, and arrival pattern. The position and speed of the vehicles are assumed to be discrete. The speed of each vehicle changes according to its interactions with other vehicles, following some stochastic rules depending on the circumstances. The model is calibrated and validated using real data and VISSIM. The results indicate that grid based model can reasonably well simulate complex heterogeneous traffic as well as offers higher computational efficiency needed for real time application.     

香港典型山区道路汽车行驶工况污染物排放研究

通过安装车载测试系统收集香港港岛山区路段正常行驶工况下尾气中的CO、NOx、HC等污染物和油耗并辅助计算机软件进行分析。研究得出,山区道路设计、地形地貌和驾驶习惯对车辆油耗以及CO、NOx和HC排放有直接关系。可以通过坡道加宽、坡道延长、减少坡道红绿灯等措施减少车辆在山区道路行驶过程中速度变化频率,从而减少油耗以及CO、NOx和HC排放。     

GPS-based speed collection method for road traffic noise mapping

One of the most difficult and expensive tasks in making noise pollution maps is the collection and processing of the data needed to create acoustic models. In the case of road traffic noise maps, obtaining speed data for light and heavy vehicles a problem that has usually been avoided by using a road’s speed limit or by making assumptions based on experience from similar road types. Here global positioning systems-based techniques are applied for acquiring vehicle speed data and adapted to fulfill the requirements of noise prediction models.     

基于驾驶员信息处理的道路安全性评价模型

在车辆行驶过程中,行车环境包含了大量的交通信息.道路条件以及管理手段等因素最终影响到驾驶员的信息处理强度.文章通过探讨驾驶员信息处理过程,建立了一种基于驾驶员信息处理强度的道路交通安全评价模型.在示例中,把道路交通信息量定义为道路几何曲率的一次函数,并结合相邻路段运行速度差给出评价指标.     

Congestion avoidance in city traffic

The number of vehicles on the road (worldwide) is constantly increasing, causing traffic jams and congestion especially in city traffic. Anticipatory vehicle routing techniques have thus far been applied to fairly small networked traffic scenarios and uniform traffic. We note here a number of limitations of these techniques and present a routing strategy on the assumption of a city map that has a large number of nodes and connectivity and where the vehicles possess highly varying speed capabilities. A scenario of operation with such characteristics has not previously been sufficiently studied in the literature. Frequent short‐term planning is preferred as compared with infrequent planning of the complete map. Experimental results show an efficiency boost when single‐lane overtaking is allowed, traffic signals are accounted for and every vehicle prefers to avoid high traffic density on a road by taking an alternative route. Comparisons with optimistic routing, pessimistic routing and time message channel routing are given. Copyright © 2014 John Wiley & Sons, Ltd.