高速公路出口匝道与地面道路衔接部的几何安全设计研究综述

高速公路出口匝道与地面道路衔接部的几何安全设计是高速公路出口匝道几何安全设计的核心内容．本文通过分析国内外出口匝道与地面道路衔接部几何安全设计研究成果,从衔接部的接入间距设计、视距设计、转弯缓冲区的设计、渠化设计和控制方式选择等方面进行了探讨,指出了我国现行规范中衔接部几何安全设计的局限性。最后,文章建议借鉴国外已有的衔接部几何安全设计的实践经验,研究适合我国国情的衔接部几何安全设计方法,为改善高速公路匝道出口区域内的交通流通行效率和交通安全提供必要的理论支撑和技术依据。     

基于梯度提升决策树的高速公路交织区汇入位置模型

匝道车辆的汇入行为对高速公路交织区的通行能力有重要的影响,汇入位置是汇入行为中最重要的行为参数之一.本文利用梯度提升决策树(GBDT)建立了一个车辆汇入位置模型并对各变量进行了分析.考虑到汇入行为是一个二维驾驶行为,我们在模型中引入了车辆进入辅助车道时的初始横向位置这一变量.利用NGSIM中的车辆轨迹数据对模型进行训练,并与Lognormal 进行对比.结果表明,GBDT模型在AIC,BIC 和R²这3个指标上均大幅优于Lognormal模型.最后,本文对解释变量的重要性和其偏效应进行了分析,其中初始横向位置的重要性最高;敏感性分析表明,GBDT模型能够深度挖掘汇入位置与变量之间隐藏的非线性关系.     

快速路分、合流影响区交通特性及通行能力研究

分、合流区通行能力是影响快速路通行能力的重要因素之一,而分、合流影响区的通行能力是制约分、合流区通行能力的关键原因。文章从分析分、合流影响区内的车辆运行特性入手,根据北京、上海、广州等城市大量的实测数据,分别通过统计车头时距、速度-流量关系和饱和流时高频率出现的流率等方法推荐了快速路分、合流影响区的通行能力,为快速路分、合流区的交通规划和设计,交通组织和管理的改善提供了理论基础。     

IEC61850-9-2标准下合并单元的研制

针对当前合并单元的研究现状,分析了合并单元的采样值映射模型IEC61850-9-2及其实现方法,在此基础上设计了一种基于现场可编程门阵列(FPGA)的合并单元装置。该装置通过在FPGA芯片上配置NiosII软核处理器和相关接口,完成合并单元同步、多路数据接收和处理以及以太网通信等功能,能满足电子式互感器数字接口的要求。     

Ground-truthing social vulnerability indices of Alaska fishing communities

Abstract

Community vulnerability is increasingly evaluated through quantitative social indices, typically developed using secondary data sources rather than primary data collection. It is necessary to understand the validity of these indices if they will be used to inform policy and decision making. This paper presents a ground-truthing effort to validate quantitative indices that characterize the well-being of Alaska fishing communities. We utilized ethnographic data collected from 13 representative communities and a capital assets framework to ground-truth the indices, in which qualitative ranks of vulnerability were compared against quantitative indices. The majority (73.8%) of ranks were in complete or moderate agreement and the results indicate that most of the indices are representative of community vulnerability; yet some variables utilized to create the indices could be modified to better reflect realities in Alaska. Indices of commercial fishery engagement and reliance appeared to be more reliable than socio-economic indicators, particularly for smaller fishing communities. We also confirmed that the indices do not capture political, or ecological factors that affect levels of community vulnerability. We conclude that quantitative indices of community vulnerability are useful rapid assessment tools; however, they should be validated, and complemented with ethnographic data prior to their implementation as policy making and management tools.     

Gap metering for active traffic control at freeway merging sections

Freeway merging sections are critical segments that can recurrently activate peak-hour traffic congestion. This article proposes a novel vehicular gap control method as a new Active Traffic Management (ATM) strategy to be added to the existing Intelligent Transportation System (ITS) toolboxes for freeway merge control. The proposed strategy, “Gap Metering,” can be considered a non-stopping mainline version of ramp metering. It utilizes signals advising mainline through vehicles to yield sufficient gaps for merging vehicles. Detailed system design and control methods are proposed and implemented in VISSIM (please spell out the abbreviation of VISSIM for this first instance), a microsimulation software package. Different driver behavior sets with different standstill headway values are created to allow switching between gap-metered vehicles and regular vehicles. We evaluate the proposed system through two VISSIM models built and calibrated, respectively, for both the I-894 corridor in Milwaukee, WI, and the Riverside Drive segment on I-35 northbound in Austin, TX. Both corridors experience severe morning peak-hour congestion. We use the I-894 corridor for testing the system design parameters and use the I-35 corridor to conduct a comparison with the ramp metering strategies. The I-894 results indicate an average of 10–20% network delay reduction among all scenarios. We then tested the scenario on the I-35 corridor and compared with the ALINEAR ramp metering. Gap metering strategies alone or combined with ramp metering can, respectively, reduce 17% and 27% more total delay than ramp metering only control at 20% compliance rate.     

Making Landfall: Linkages between Fishing Communities and Support Services

The relationship between the fishing industry and the fisheries-related support service sector creates economic benefits for communities through the strong linkages between fishermen and their land-based suppliers and the induced or multiplier effects from fisheries revenue. The support service sector is embedded within fishing communities where the impacts of fisheries management changes are perpetuated. This article examines the potential for such impacts by evaluating the diversity of fishing gear use, ex-vessel revenue, presence of processing plants, public moorage, and haul-out or tidal grids, and the number of vessels in a community, in relation to the availability of support services in communities in Alaska. The results show that the presence of a processor and haul-out facilities in a community significantly affects the number of support service businesses; however, there is not a strong association with the number of vessels or ex-vessel revenue. One hypothesis is that fishermen often travel to other communities to obtain services. We evaluate this hypothesis using social network analysis to evaluate transfers of revenue for fishery-related goods and services. Ultimately, this informs the exploration of the importance of support service businesses and fishery-support infrastructure to the continued well-being of fishing communities.     

基于BP神经网络的高速公路入口合流区域换道行为研究

为了应对高速公路入口合流区域并线事故频繁发生,在分析车辆并线行为影响因素的基础上,利用BP神经网络方法建立了车辆在该区域的决策模型,用来预测驾驶人的并线行为决策,保障车辆和驾驶人的安全.借助详细的车辆轨迹数据对模型进行了学习与测试,模型的测试结果表明:建立的BP神经网络模型用于预测驾驶人并线行为具有较高的准确度,并线车辆相对于目标车道前方车辆的相对速度是驾驶人并线时需要考虑的最重要因素.同时模型还可以进一步应用于交通仿真的研究以及驾驶人辅助系统的开发.