加法与减法——中美城市交通综合治理的观察和思考

基于对中美城市交通的观察和思考,阐述不同的城市用地模式决定了不同的大众出行方式选择。借鉴美国的经验与教训,结合中国城市现状和发展需要,寻求缓解城市交通拥堵的方法与措施。指出中国大城市,特别是特大和超大城市,应重视公共交通系统的结构调整和完善。一是继续大力发展具有较高机动性和大运量的高铁、地铁和轻轨系统,构筑城际直达以及沿主要交通走廊布线的轨道交通网络层次;二是在此基础上,梳理地面巴士系统,使之定位于满足可达性需求的支线集散网络层次。最后,还探讨了其他一些相关措施,以减少低速、低效出行,做好综合治理城市交通的"加法"与"减法"。     

Efficient missing data imputing for traffic flow by considering temporal and spatial dependence

The missing data problem remains as a difficulty in a diverse variety of transportation applications, e.g. traffic flow prediction and traffic pattern recognition. To solve this problem, numerous algorithms had been proposed in the last decade to impute the missed data. However, few existing studies had fully used the traffic flow information of neighboring detecting points to improve imputing performance. In this paper, probabilistic principle component analysis (PPCA) based imputing method, which had been proven to be one of the most effective imputing methods without using temporal or spatial dependence, is extended to utilize the information of multiple points. We systematically examine the potential benefits of multi-point data fusion and study the possible influence of measurement time lags. Tests indicate that the hidden temporal–spatial dependence is nonlinear and could be better retrieved by kernel probabilistic principle component analysis (KPPCA) based method rather than PPCA method. Comparison proves that imputing errors can be notably reduced, if temporal–spatial dependence has been appropriately considered.     

Surface street traffic volume and single-family house price

This study investigates the relationship between surface street traffic volume and single-family house prices in a relatively small city in the US. Hedonic price models are estimated using data from 9670 transactions that occurred between January 1998 and March 2011. It is discovered that parcels fronting or adjacent to a high-traffic street sell, on average, at an 8.1% discount compared to similar parcels that are not so situated. Restricting the analysis to parcels on or adjacent to a high-traffic street, house price and traffic volume are found to be negatively related; a doubling of volume from any particular traffic count, ceteris paribus, reduces selling price by an average of 2.1%.     

基于集对分析的道路交通拥堵判定

基于集对分析原理提出了道路交通拥堵判定的新方法——集对分析法,给出了集对分析法的基本思路和交通拥堵判定步骤。该方法考虑了交通状态分级标准的模糊性,同时避免了差异不确定系数的取值,应用于成都市某路段交通拥堵状态的判定,结果表明,该方法概念清晰、结构简单、计算简单、易操作、可行有效。     

Modeling the Car-Truck Interaction in a System-Optimal Dynamic Traffic Assignment Model

Several transportation problems, such as implementation of truck-only lanes, require understanding the interaction of heterogeneous dynamic traffic flows in order to provide accurate solutions. System-optimal dynamic traffic assignment can be modeled using a network loading procedure based on the cell transmission model, that is, the hydrodynamic wave model, and solved by linear programming. However, this framework cannot handle the asymmetric integration between the flow of trucks and cars. This article presents a novel formulation for network loading in system-optimal dynamic traffic assignment considering car–truck interactions. By using an embedded cell transmission model, this formulation incorporates a set of assumptions related to the kinematic characteristics of the flow of cars, trucks, and their interactions that can be solved using linear programming. We present numerical results supporting our modeling assumptions. Likewise, the observed emergent behavior captures the car–truck interactions accurately and indicates that minimum system-optimal travel time is obtained by encouraging cars to use highways with shorter distances.     

Did California’s hand-held cell phone ban reduce accidents?

On July 1st, 2008, California enacted a ban on hand-held cell phone use while driving. Using California Highway Patrol panel accident data for California freeways from January 1st, 2008 to December 31st, 2008, we examine whether this policy reduced the number of accidents on California highways. To control for unobserved time-varying effects that could be correlated with the ban, we use high-frequency data and a regression discontinuity design. We find no evidence that the ban on hand-held cell phone use led to a reduction in traffic accidents.     

变形车辆自标定三维重建的建模研究

变形车辆测量是道路交通事故再现的重要基础性工作。建立基于普通数码相机的事故变形车辆自标定三维重建模型,可以避免在现场设置标定物,有利于提高变形车辆的勘测效率和三维重建设备的使用方便性。研究了基于基础矩阵估计的事故变形车辆摄影图像自标定三维模型,并分析了其实现过程。实验表明,自标定三维重建能为事故再现提供详细的车辆变形描述。     

多模式拥挤交通网络中的路径分配与收费定价模型

根据城市混合交通拥挤的特点,提出了在收费路段对不同的交通方式收取不同费用,以此控制各种交通方式的分担量,鼓励人们更多地选用公共的交通工具,从而达到缓解交通拥挤的目的,并以此为出发点建立了一个关于多模式收费定价的双层规划模型.     

山区高速公路隧道典型安全因素分析及其对策研究

文章针对西部多条山区高速公路隧道运营安全情况,分析山区高速公路隧道的典型安全事故及原因,提出了基于车速限制、车道限制、照明控制与交通安全设施的安全对策,为山区高速公路隧道的安全运营提供参考。     

汽车-行人撞击事故过程仿真研究

根据中国人体特征参数建立了16刚体的行人模型,在人体的主要部位生成简易的弹簧阻尼运动关节。建立汽车模型与汽车行人碰撞模型,应用ADAMS软件模拟汽车行人碰撞过程。通过模拟不同速度下的汽车人体撞击,对事故发生过程进行再现,比较仿真数据和事故现场数据得到了事故中的汽车速度,从而为交通事故提供了一种有效的处理方法。