A speed-flow relationship model of highway traffic flow

In the view that the generally used speed-flow relationship model is insufficient in the traffic analysis under over-saturated conditions, this paper first establishes the theoretical models of speed flow relationship for each highway class based upon a large number of traffic data collected from the field. Then by analyzing the traffic flow dissipation mechanism under peak hour over-saturated traffic conditions, the speed flow relationship model structures for each highway class are reviewed under different traffic load conditions. Through curve-fitting of large numbers of observed data, functional equations of general speed-flow relationship models for each highway class under any traffic load conditions are established. The practical model parameters for each highway class under different design speeds are also put forward. This model is successful in solving the speed-forecasting problem of the traffic flow under peak hour over-saturated conditions. This provides the theoretical bases for the development of projects related to highway network planning, economic analysis, etc.     

A Model for Capacity Considering the Interference by Pedestrian Traffic at Signal Intersections

The capacity is impacted badly by pedestrians’ violation behavior at signal intersections. In order to quantify the impact, the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis, the time-headway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians’ influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time, the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14% at the worst case (level I ). The conclusions obtained in this paper are valuable for better management of the signal intersection.     

一个细化的无胞自动机模型中的加速度和随机慢化效应及其与同步流可能的联系(英文)

The effect of acceleration a and randomization D in a refined Nagel-Schreckenberg traffic flow model is investigated.It is found that when a≥D,there is no qualitative change of the fundamental diagram and spatiotemporal pattern.In contrast,when a相似文献   

Analysis and study of a handoff scheme with multiple priority strategies

A handoff scheme with the combination of channel reservation and preemptive priority in integrated voice/data cellular mobile systems is proposed. In the scheme, calls are divided into three different classes: handoff voice calls, originating voice calls, and data calls. An access strategy with the combination of channel reservation and preemptive priority is provided to a handoff voice call. Furthermore, in order to improve the system capacity for the total voice traffic, preemptive priority is also given to partial originating voice calls. The system is modeled by a two-dimensional Markov chain. Both the iteration method and the approximate method are used to calculate and analyze some of the most important performance measures of the system. It is shown that our scheme can provide better quality of services for mobile subscribers.     

Road network extraction in classified SAR images using genetic algorithm

Due to the complicated background of objectives and speckle noise, it is almost impossible to extract roads directly from original synthetic aperture radar(SAR) images. A method is proposed for extraction of road net-work from high-resolution SAR image. Firstly, fuzzy C means is used to classify the filtered SAR image unsupervis-edly, and the road pixels are isolated from the image to simplify the extraction of road network. Secondly, according to the features of roads and the membership of pixels to roads, a road model is constructed, which can reduce the extraction of road network to searching globally optimization continuous curves which pass some seed points. Final-ly, regarding the curves as individuals and coding a chromosome using integer code of variance relative to coordi-nates, the genetic operations are used to search global optimization roads. The experimental results show that the al-gorithm can effectively extract road network from high-resolution SAR images.     

Threshold values of traffic flow for the provision of exclusive bus lanes

A simulation network model was established using VISSIM software and verified by the Ttest. The model took into consideration the road conditions,pedestrian crossing,traffic composition,bus stops and traffic signal. The operating characteristics of buses and cars under different flow conditions were studied using the simulation model,and the speed-flow models of buses and cars were established based on the simulation results. Finally,the threshold values of traffic flow for the provision of exclusive bus lanes was determined with the target of optimal travel benefits( per capita),which would provide a basis for the planning and design of exclusive bus lanes on urban roads.     

Road traffic states estimation algorithm based on matching of regional traffic attracters

To effectively solve the traffic data problems such as data invalidation in the process of the acquisition of road traffic states, a road traffic states estimation algorithm based on matching of the regional traffic attracters was proposed in this work. First of all, the road traffic running states were divided into several different modes. The concept of the regional traffic attracters of the target link was put forward for effective matching. Then, the reference sequences of characteristics of traffic running states with the contents of the target link＇s traffic running states and regional traffic attracters under different modes were established. In addition, the current and historical regional traffic attracters of the target link were matched through certain matching rules, and the historical traffic running states of the target link corresponding to the optimal matching were selected as the initial recovery data, which were processed with Kalman filter to obtain the final recovery data. Finally, some typical expressways in Beijing were adopted for the verification of this road traffic states estimation algorithm. The results prove that this traffic states estimation approach based on matching of the regional traffic attracters is feasible and can achieve a high accuracy.     

Cloud Computing Based Optimal Driving for a Parallel Hybrid Electric Vehicle

A cloud computing based optimal driving method is proposed and its feasibility is validated through a real-world scenario simulation. Based on principles of vehicle dynamics, the driving optimization problem has been formulated into an optimal control problem constrained by traffic rules, directed at achieving lower equivalent fuel consumption and shorter travel time. In order to conveniently specify the constraints and facilitate the application of the dynamic programming (DP) algorithm, the driving optimization problem is transformed into spatial domain and discretized properly. Considering the heavy computational costs of the DP algorithm, a cloud computing based platform structure is proposed to solve the optimal driving problem in real-time. A case study is simulated based on a real-world traffic scenario in Matlab. Simulation results demonstrate that the cloud computing framework is promising toward realizing the real-time energy management for hybrid electric vehicles.     

Contention avoidance using dual-fuzzy assembly threshold algorithm in optical burst switching networks

To avoid burst contention efficiently,on the basis of feedback-based source flow-rate control(SFC) strategy,a novel fuzzy-control-based assembly algorithm,called dual-fuzzy assembly threshold(DFAT),is proposed in an optical burst switching network.In our algorithm,according to the variations of burst assembly period and the interarrival of burst control packet,the traffic states of edge-switching nodes and core-switching nodes are first obtained.Then,the assembly threshold of bursts is set dynamically in order to operate the source traffic management from the information of traffic states.The performance of DFAT algorithm on burst loss probability is evaluated,and simulation results show that,compared with conventional assembly algorithms,the proposed scheme can constrain the birth of burst contention efficiently,when being a heavy load state of network.     

Influence of Skidding Operation on Forest Soil Respiration for Small Four-wheeled Tractors

The TJSD-750-Ⅱ type compactness measurement instrument and Li-8100 soil carbon flux automatic measurement system are used to measure soil compactness and soil respiration rate at different skidding roads. A regression model is established to analyze the correlation between soil respiration and its influencing factors. The results shows that the soil compaction on the main skidding road and sub skidding roads are larger than the control points, and the soil compaction on the main skidding road is larger than that on sub skidding roads. The higher the soil compactness is, the lower the rate of soil respiration is. This also leads to the lower sensitivity of soil respiration rate influenced by temperature and humidity.     

交通环境对道路安全影响的定量评价

为了定量评价交通环境因素对道路安全带来的影响,提出了模糊一致矩阵法。针对2条高速公路4个相似路段道路安全事故的标准事故值建立了评价矩阵,计算评价了对象的优属度值,对其安全问题进行了评价。结果表明:该方法能够定量直观地表达评价结果,是定量评价交通环境对道路安全影响的有效方法。     

高速公路交通安全的影响因素及预防途径

通过分析高速公路交通事故的现状及特点 ,分别从人、车、路三方面探讨了诱发交通事故的原因。并结合我国的交通现状 ,提出了交通事故的预防途径 ,对在高速公路上行驶的车辆如何减少和预防交通事故的发生 ,将起到一定的警示、借鉴作用     

利用面板数据的高速公路安全分析

随着汽车保有量的增加,交通事故已成为威胁人们生活的安全隐患．使用Paneldata模型进行不同路段交通事故的统计回归分析．分别介绍了个体固定效应模型和随机效应模型的建立过程以及相关检验,并应用于京津塘高速公路的事故分析．Hausman检验表明,个体固定效应回归模型更加合理、适合于高速公路事故分析．同时可识别路段间的差异,快速定位事故高发路段．     

基于汽车速度分布的道路安全评价分析

道路的安全评价研究通常是根据道路的交通事故统计数据来进行,难以在道路勘测、设计和施工之前有效地对道路的安全性进行评价.本课题的主要研究内容是在驾驶模拟器上建成相关道路的虚拟场景,通过驾驶员在驾驶模拟器上驾驶试验,获取道路沿线的速度,然后以速度轨迹和速度均方差作为基础,分析线形对道路安全的影响规律,并对设计道路的安全性进行研究.     

菱形立交分流区主线线形指标分析

为确定菱形互通式立交分流区域主线线形指标,分析了菱形互通式立交分流处的交通事故特征,运用汽车理论、交通心理学及人机工程学获取菱形立交分流区的识别视距,运用VB程序开发软件及高速公路横净距设置条件建立菱形立交区域主线平面及纵断面指标和识别视距关系模型,提出菱形立交分流区满足识别视距要求的主线圆曲线半径及凸形竖曲线半径值.结果表明:对待建菱形立交分流区应分析识别视距,并用识别视距对主线线形指标验算;对已建成菱形立交分流区,应加强安全保障措施,保证主线及驶离主线车辆行车安全.     

道路交通事故人-车-道路环境系统分析

本文通过对我国现阶段的道路交通事故的统计分析，提出了减少道路交通事故。必须从人-车-道路环境系统的各个环节进行人机分析，强调在整个系统中除解决人的驾驶适宜性和驾驶室的宜人性设计外，还着重强调了人-车-道路系统的协调性，并指出了目前尚未引起重视的道路设计．     

北京市城乡结合部公路高风险区域成因分析

基于交通部西部项目"公路交通安全数据库"GIS平台的相关数据,以北京市通州区为例,采用"空间数据分析"的方法,以千万车公里事故率为依据对通州区公路交通安全服务水平进行划分,并以此分析公路高风险区域形成原因,给出治理办法.     

中小交通量旅游公路休息区设计研究

在公路沿线合理布设休息区,供车辆停靠和司乘人员休息,有利于保障交通安全.本文借鉴高速公路服务区设计和部分服务旅游交通出行的公路观景台设计经验,从交通工程设施设计和交通管理的角度,针对中小交通量旅游公路休息区的选址、基本形式、功能定位以及相关设施的总体平面布设等问题,以内蒙古林区旅游公路S203线为例进行了论述.文中所提及的设计理念、原则和方法,可以为我国同类旅游公路休息区的设计提供参考.     

基于广义线性模型交通事故损失影响因素研究

综合考虑车龄、驾龄、车辆座位数等特征参数,利用广义线性模型分析技术,建立多元广义线性模型对以上影响因素与交通事故二者之间的内在关联性进行研究。结果表明:广义线性模型能对交通事故的风险因素进行风险分组,并明确易发生交通事故的群体。因此,可以把该系统应用于交通事故管理,确保驾驶的安全性和行驶的有效性。     

基于Ward聚类法的道路交通事故多元统计分析

道路交通事故具有空间分布规律,不同地区有所差异。在选取道路交通事故统计指标的基础上,基于系统聚类分析的基本原理,采用Ward最小方差平方和法对某地区道路交通安全状况进行聚类分析。通过分类,将具有共性的地区划归为一类。结果表明,类别的划分突出特性,反映道路交通事故具有空间分布特征,有助于掌握道路交通安全状况,便于采取相应的防治措施。