城市道路与汽车保有量相互关系研究

城市交通是城市最主要功能之一，近年随着我国城市化、城市交通机动化加快及汽车工业的发展，我国大中型城市开始面临日益严重的交通问题。本文在对我国城市交通现状进行整体分析的基础上，结合城市道路情况及城市建设布局对交通的影响，研究人，车、路之间的关系，将针对国内城市道路发展潜力，评估其对汽车进入人民生活的影响。     

城市道路与汽车保有量相互关系研究

本文在对我国城市交通现状进行整体分析的基础上，结合城市道路情况及城市建设布局对交通的影响，研究人、车、路之间的关系。     

城市道路与汽车保有量相互关系研究

城市交通是城市最主要的功能之一。近年来,随着我国城市化、城市交通机动化的加快及汽车工业的发展,我国大中型城市开始面临日益严重的交通问题。本文在对我国城市交通现状进行整体分析的基础上,结合城市道路情况及城市建设布局对交通的影响,研究人、车、路之间的关系,将针对国内城市道路发展潜力,评估其对汽车进入人民生活的影响。     

汽车保有量与年产量的神经网络预测研究

采用神经网络建立汽车保有量与年产量时间序列的预测模型，并对我国未来几年的汽车保有量和年产量进行预测，其中包括民用汽车拥有量、私人汽车拥有量和汽车产量等，取得了较为满意的预测结果，对预测结果进行分析，指出了我国汽车保有量与产量今后发展的特点和趋势。     

全球汽车保有量与中国汽车保有量

据美国汽车行业权威杂志Wardsauto公布： 根据各国和地区政府公布的汽车注册量及历史上汽车保有量,截至2011年8月16日,全球处于使用状态的各种汽车,包括轿车、卡车以及公共汽车等的总保有量已突破10亿辆,其中中国增速世界第一。     

我国汽车保有量的分析与预测

汽车运输作为现代交通运输的五大方式之一，相比铁路、水路、航空和管道运输等四大运输方式来说，它具有机动灵活，速度快，货损小，以及门对门的直达运输等特点，特别是高谏公路、集装箱运输业、以及家用小轿车的发展，使得汽车运输在交通运输中占有主导地位。发达国家汽车运输量一般占运输总量的80％以上，并且这一比例还在不断上升。我国汽车工业前40年发展缓慢，目前汽车运输量只占运输总量的61％。1993年底我国各类汽车保有量为81O万辆，只相当于美国的1／28，日本的1／10，德国的1／6，英、法、意的1／4左右。显然，我国汽车保有量是…     

我国未来汽车保有量情景预测研究

汽车保有量的预测具有一定程度的不确定性。对2010、2020及2030年我国的汽车保有量进行科学预测,是确定我国公路交通长短期发展规划,制定环保与能源等方面相关政策的关键。在对我国经济各个发展阶段进行情景分析的基础上,考虑经济、人口、汽车保有量增长速度以及不同地区人均GDP人群分布等因素,运用趋势外推、弹性系数、国内外情景类比及运输工作量计算等方法对我国未来的汽车保有量进行综合预测,确定到2030年我国汽车保有量将达到2.3~2.5亿辆,是2020年的1.7~1.9倍左右、是2010年的4.6倍。汽车保有量的大幅度增加势必对土地、能源资源和环境保护带来巨大压力,贯彻科学发展观、节约资源、保护环境,走可持续发展道路将是我国未来道路交通发展的客观要求。     

中国新能源汽车总保有量超万辆

日前在北京召开的节能与新能源汽车示范推广工作会议明确。截至目前,25个试点城市节能与新能源汽车总保有最超过1万辆,其中私人购买新能源汽车超过1千辆．建成充、换电站近100座。充电桩4500多个,示范运行总里程超过33000万公里。会议强调,新能源汽车是汽车产业发展的方向．已被列为战略性新兴产业,新能源汽车发展耍尽快向产业化推进。要加强技术研发,不断提高我国新能源汽车产业的整体水平。     

上半年全国机动车保有量保持快速增长,11城市汽车保有量过百万

随着我国社会经济快速发展和人民生活水平不断提高,汽车化进程不断加快,机动车消费需求旺盛。据统计,截至2011年6月底,全国机动车总保有量达2.17亿辆。其中,汽车9846万辆,摩托车1.02亿辆。11城市汽车保有量过百万。上半年,全国新增机动车1005万辆。其中,汽车保有量增加760万辆,高于2010上半年688万辆的增量。     

灰色系统用于汽车保有量与年产量的预测研究

分析了灰色系统的方法用来预测的特点，采用ＧＭ（１，１）方法分别对我国未来若干年的汽车保有量和年产量进行预测，其中包括民用汽车用量，私人汽车量和汽车产量等，取得了好的预防测效果。对预测结果进行分析，指出了我国的汽车保有量和产量今后发展的特点和趋势。     

中国城市公交和车辆技术的创新发展

本文对中国城市公交和车辆技术的创新发展最新成果进行了介绍，论述了中国城市公交和车辆技术的发展方向及发展前景。     

Autonomous vehicle self-localization based on abstract map and multi-channel LiDAR in urban area

Accurate vehicle self-localization is significant for autonomous driving. The localization techniques based on Global Navigation Satellite System (GNSS) cannot achieve the required accuracy in urban canyons. On the other hand, simultaneous localization and mapping (SLAM) methods suffer from the error accumulation problem. State-of-the-art localization approaches adopt 3D Light Detection and Ranging (Lidar) to observe the surrounding environment and match the observation with a priori known 3D point cloud map for estimating the position of the vehicle within the map. However, storing the massive point cloud needs immense storage on the vehicle, or it should be stored on servers, which makes the simultaneous downloading of the map by multiple vehicles another challenge. In this study, rather than employing the point cloud directly as the prior map, we focus on the abstract map of buildings, which is easy to extract, and at the same time apparently observable by Lidar. More especially, we proposed vehicle localization methods based on two different abstract map formats representing urban areas. The first format is the multilayer 2D vector map of building footprints, which represents the building boundaries using vectors (lines). The second format is the planar surface map of buildings and ground. These map formats share the same idea that the uncertainty (deviation) of each vector or planar surface is calculated and included in the map. Later in the localization phase, the observed data from Lidar is matched with the abstract map to obtain the precise location of the vehicle. Experiments conducted in a dense urban area of Tokyo show that even though we significantly shrank the map size, we could preserve the mean error of the localization.     

Integration of GPS and monocular vision for land vehicle navigation in urban area

For land vehicle navigation in urban area, Global Positioning System (GPS) receivers often suffer from the lack of positioning accuracy, availability, and continuity due to insufficient number of visible satellites and multipath errors. To mitigate this problem, this paper proposes an efficient hybrid positioning method combining a single frequency GPS receiver and a monocular vision sensor. The proposed method is advantageous in that it requires only low-cost hardware and no external map aiding. Compared with existing vision-based methods, the proposed method directly measures absolute heading angle based on the images of straight road segments. For the reason, the proposed method is resilient to multipath errors. The performance of the proposed method is evaluated by the experiments with field-collected real measurements; one with good satellite visibility and the others with poor satellite visibility. Comparison with existing positioning methods demonstrates the feasibility of the proposed method in urban area.     

A weight-based map-matching algorithm for vehicle navigation in complex urban networks

A map-matching algorithm is an integral part of every navigation system and reconciles raw and inaccurate positional data (usually from a global positioning system [GPS]) with digital road network data. Since both performance (speed) and accuracy are equally important in real-time map-matching, an accurate and efficient map-matching algorithm is presented in this article. The proposed algorithm has three steps: initialization, same-segment, and next-segment. Distance between the GPS point and road segments, difference between the heading of the GPS point and direction of road segments, and difference between the direction of consecutive GPS points and direction of road segments are used to identify the best segment among candidates near intersections. In contrast to constant weights applied in existing algorithms, the weight of each criterion in this algorithm is dynamic. The weights of criteria are calculated for each GPS point based on its: (a) positional accuracy, (b) speed, and (c) traveled distance from previous GPS point. The algorithm considers a confidence level on the assigned segment to each GPS point, which is calculated based on the density and complexity of roads around the GPS point. The evaluation results indicate 95.34% correct segment identification and 92.19% correct segment assignment. The most important feature of our algorithm is that the high correct segment identification percentage achieved in urban areas is through a simple and efficient weight-based method that does not depend on any additional data or positioning sensors other than digital road network and GPS.     

Investigation on dynamical interaction between a heavy vehicle and road pavement

This paper presents a model for three-dimensional, heavy vehicle-pavement-foundation coupled system, which is modelled as a seven-DOF vehicle moving along a simply supported double-layer rectangular thin plate on a linear viscoelastic foundation. The vertical tyre force is described by a single point-contact model, while the pavement-foundation is modelled as a double-layer plate on a linear viscoelastic foundation. Using the Galerkin method and quick direct integral method, the dynamical behaviour of the vehicle-pavement-foundation coupled system is investigated numerically and compared with that of traditional vehicle system and pavement system. The effects of coupling action on vehicle body vertical acceleration, suspension deformations, tyre forces and pavement displacements are also obtained. The investigation shows that the coupling action could not be neglected even on a smooth road surface, such as highway. Thus, it is necessary to investigate the dynamics of vehicle and pavement simultaneously based on the vehicle-pavement-foundation coupled system.     

项目开发与交通系统协调度评价

在交通影响评价的基础上,充分考虑交通的可持续发展,从项目的建设对交通和环境两方面的影响进行分析,不仅考虑了项目的开发对交通系统承载力上限的影响,还考虑了交通系统资源的充分利用问题以及经济性问题,即项目开发与交通系统的协调度。为了便于操作,同时又多方考虑系统内的各种影响因素,本文采取基于AHP的模糊综合评判方法进行评价。     

Effect of vertical and lateral coupling between tyre and road on vehicle rollover

The vehicle stability involves many aspects, such as the anti-rollover stability in extreme steering operations and the vehicle lateral stability in normal steering operations. The relationships between vehicle stabilities in extreme and normal circumstances obtain less attention according to the present research works. In this paper, the coupling interactions between vehicle anti-rollover and lateral stability, as well as the effect of road excitation, are taken into account on the vehicle rollover analysis. The results in this paper indicate that some parameters influence the different vehicle stabilities diversely or even contradictorily. And it has been found that there are contradictions between the vehicle rollover mitigation performance and the lateral stability. The direct cause for the contradiction is the lateral coupling between tyres and road. Tyres with high adhesion capacity imply that the vehicle possesses a high performance ability to keep driving direction, whereas the rollover risk of this vehicle increases due to the greater lateral force that tyres can provide. Furthermore, these contradictions are intensified indirectly by the vertical coupling between tyres and road. The excitation from road not only deteriorates the tyres’ adhesive condition, but also has a considerable effect on the rollover in some cases.     

Rail vehicle wheel wear prediction: a comparison between analytical and experimental approaches

There are a number of theoretical and practical techniques to compute rail vehicle wheel wear. For instance, the Archard equation is a well-known tool to determine the worn volume in sliding contact, as a function of normal load, sliding distance and the surface hardness. Of course, the wear coefficient (called K) used in this equation to differentiate the wear models implicitly comprises the conditions that govern the contact surface. Two situations can be taken into account when considering a sliding contact in a rail vehicle wheels, particularly along a curved track: (i) when the radial force prevails the lateral tangential force, which is mainly the frictional force but before flanging and (ii) during flange contact. Also, the Archard equation is employed within the tread and flange regions separately, both the regions being of interest in this paper. A number of approaches are then used to find the distance slid. The authors compare the field test results and the outcome of the analytical approaches. When the wheel wear results acquired from the two test bogies on Iranian Railways, all technical (rigid frame bogies with new assemblies and components) and operational items were identical, except for changing the bogie orientation in the second test trial for a short period. Good agreement was found between the analytical and practical investigations.