Bus Priority Using pre-signals

The need to provide efficient public transport services in urban areas has led to the implementation of bus priority measures in many congested cities. Much interest has recently centred on priority at signal controlled junctions, including the concept of pre-signals, where traffic signals are installed at or near the end of a with-flow bus lane to provide buses with priority access to the downstream junction. Although a number of pre-signals have now been installed in the U.K., particularly in London, there has been very little published research into their design, operation and optimisation. This paper addresses these points through the development of analytical procedures which allow pre-implementation evaluation of specific categories of pre-signals. The paper initially sets out three categories of pre-signal, which have different operating characteristics, different requirements for signalling and different impacts on capacity and delay. Key issues concerning signalling arrangements for these categories are then discussed, together with a summary of the analytical approach adopted and the assumptions required. Equations are developed to allow appropriate signal timings to be calculated for pre-signalised intersections. Further equations are then developed to enable delays to priority and non-priority traffic, with and without pre-signals, to be estimated with delay being taken here as the key performance criterion. The paper concludes with three application examples illustrating how the equations are applied and the impacts of pre-signals in different situations.The analyses confirm the potential benefits of pre-signals, where these signals apply to non-priority traffic only. Where buses are also subject to a pre-signal, it is shown that disbenefits to buses can often occur, unless bus detectors are used to gain priority signalling.     

快速公交专用车道及站台布设模式选择

专用车道和站台是快速公交系统（BRT）重要的设施要素,对其布设模式进行了研究。从3种典型的布设模式入手,即中央专用车道＋岛式站台、中央专用车道＋侧式站台、路侧专用车道＋侧式站台,分析其规划设计要点、模式优缺点、适用性等。总结快速公交系统规划过程中影响专用车道及站台布设模式选择的因素,包括BRT在城市中的功能定位、道路条件、交通量等方面。以南宁市快速公交线网规划中专用车道及站台的规划设计为例,对其布设模式选择、专用车道及站台的布设进行分析。     

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排队长度作为评价信号交叉口运行效率的一个重要指标,能有效反映交叉口处的运行状况.传统排队检测模型大多基于线圈检测器,且模型假设过于理想化,本文提出一种面向低采样率浮动车数据、具有良好数据驱动性的信控交叉口在线排队长度检测方法,方法关键在于利用队尾浮动车位置估算最大排队长度.检测过程采用固定时间间隔,主要步骤包括地图匹配、等距划分交叉口进口道并统计停车点数量、判定队尾浮动车的位置、修正得到最大排队长度估计值.实测数据表明,此方法的精度与浮动车比率有直接的关系,在浮动车比率较高的许多主干路交叉口,精度可以达到理想效果,30 m以内的平均绝对误差对高峰期的排队检测依旧具有很大价值.     

公交专用道停靠站通行能力模型分析

为了更准确地计算公交专用道停靠站通行能力,以道路通行能力理论为基础,分析影响停靠站通行能力的关键因素,对该模型提出优化和调整,并通过实例分析进行验证,得出符合中国实际情况的公交专用道停靠站通行能力改进模型.     

应用于换道预警的驾驶风格分类方法

针对不同驾驶风格驾驶人对换道预警需求存在差异的问题,采用视觉传感器、 雷达传感器、GPS、车辆 CAN 总线数据采集系统,基于小型乘用车搭建了实际道路驾驶行 为试验车.通过对多名驾驶人进行实际道路自然驾驶试验,选用跟车时距、换道时距、超速 频次、换道过程最大方向盘转角等参数,采用模糊评价法建立了驾驶风格离线分类模型, 实现了将驾驶人分类为冒进型、比较冒进型、比较谨慎型、谨慎型四类.采用换道安全性相 关参数对模型进行验证. 结果表明,随着驾驶人谨慎程度的增加,换道安全性评价参数更 倾向于安全,驾驶风格分类模型与实际换道安全性评价参数之间呈现良好的一致性.     

A proposed vision and vehicle-to-infrastructure communication-based vehicle positioning approach

It is essential to obtain accurate location of vehicles for new applications of Intelligent Transportation Systems. To remedy the defects of present Global Positioning System and vehicle-to-infrastructure (V-I) positioning technology, a new positioning approach based on vision and V-I communication is proposed. This approach aims at lane-level positioning with lower cost than conventional ones. In this approach, the position of the vehicle is represented by its lateral position (the lane number) and longitudinal position (the distance from entrance of the road) in a course coordinate system along the road; the specific lane the vehicle is occupying (the lane number) can be judged using the information of lane lines detected by vision systems; then the distance to the vehicle is obtained by a Road Side Unit (RSU) during the V-I communication; and the longitudinal position is calculated. The error of the approach on typical operating conditions is analyzed, indicating that the new approach can achieve the accuracy of less than 0.31 m for straight road and 0.58 m for typical arc road with ultra-wideband communication and ranging technologies and rational arrangement of RSUs. The feasibility of this approach is presented.     

武汉光谷国际网球中心与三环线衔接匝道研究

介绍了武汉市三环线武黄立交新增匝道的设计思路、方案调整及匝道车道数研究。通过分析新增匝道建设的主要受控因素,提出了三环线到达及驶离网球中心停车场不同路径的匝道方案,并从多方面对匝道方案进行综合比选。     

The “field of safe travel” revisited: interpreting driving behaviour performance through a holistic approach

The present paper proposes a conceptual framework for the driver’s visual–spatial perceptual processes. Based on a theoretical analysis of driving proposed by Gibson and Crooks [(1938). A theoretical field-analysis of automobile-driving. The American Journal of Psychology, 51, 453–471. doi:10.2307/1416145], the developed field of safe travel (FoST) framework suggests that at any moment the driver constructs a “field” by integrating two perceptual entities: (i) the possible available spatial fields for locomotion and (ii) the driver’s mental image of ego-vehicle outer-line and motion dynamics. This framework is used to reinterpret in a unified way a number of disparate research findings reported in the literature concerning specific driving sub-tasks (e.g. lane keeping and car following). It is argued that the FoST framework may be used to predict drivers’ behaviour in various traffic/situation environments based on their prioritisation between the above two perceptual entities. Implications of the proposed framework at a theoretical and practical level, in view of the future of driving with multiple levels of automation, are also discussed.     

Predicting queue variability to enable analysis of overload risk

ABSTRACT

Predicting the risk of traffic demands and delays exceeding critical limits at road junctions, airports, hospitals, etc., requires knowing how both mean and variance of queue size vary over time. Microscopic simulation can explore variability but is computationally demanding and gives only sample results. A computationally efficient approximation to the mean is used in many modelling tools, but only empirical extensions for variance in particular situations have been available. The paper derives theoretical formulae for time-dependent and equilibrium variance, believed to be novel and to apply generally to queues covered by the Pollaczek–Khinchin mean formula, and offering possible structural insights. These are applied in an extended approximation giving mutually consistent mean and variance estimates with improved accuracy. Tests on oversaturated peak demand cases are compared with Markov probabilistic simulation, demonstrating accuracy (R^2?>?0.99) for typical random, priority-like (M/M/1) and traffic-signal-like (M/D/1) queues. Implications for risk analysis, planning and policy are considered.     

Safety modeling for two‐way left‐turn lanes and a procedure to identify two‐way left‐turn lane segments with safety concerns

In the past, two‐way left‐turn lane (TWLTL) median treatments have been frequently used in Florida to inexpensively improve traffic and safety performances. In order to identify factors that may have significant impacts on safety operations in TWLTL sections and to identify TWLTL locations that present existing and future safety concerns, a research project was carried out and results are summarized in the paper. In the research, a three‐year crash history database with crashes and section characteristics from a total of 1688 TWLTL sections all over Florida was developed and used. A negative binomial regression model was developed to determine the statistical relationship between the number of crashes per mile per year and several variables such as traffic volume, access density, posted speed, and number of lanes. In regard to the methodology, in order to identify locations with safety concerns, several steps are needed: development of real crash data distribution, determination of statistical distribution models that better represent the actual crash data, determination of percentile values for the average number of crashes, estimation of crash rates for sections with the same characteristics, estimation of critical values for the variables corresponding to the percentile values for average number of crashes, calculation of tables of critical average annual daily traffic values, and generation of a list of TWLTL locations with critical safety concerns. Results presented in the paper have been used in real applications. Copyright © 2012 John Wiley & Sons, Ltd.