需求信息的延迟对牛鞭效应的影响

研究在一个库存环境中,用于未来需求预测的需求信息的延迟对于需求预测的影响.当通过一种补充订货策略控制补货时,这种延迟降低了历史订单信息的波动性,最终减弱了牛鞭效应的影响.     

大型活动广场访客聚集行为控制指标研究

通过大型活动广场访客聚集行为特性分析，指出当访客人次数远超过设计访客指标值时，为了降低参观人流聚集风险，广场最小人均占有空间值可以作为实现高聚集效应向中等聚集效应转换的关键交通控制指标．结合多次实地调查，采用统计分析技术，确定安全集散条件下，入口排队广场最小人均占有空间值的合理取值。     

车辆离散特性研究及仿真

针对目前有关分车道行驶的方案,对不同车辆行驶速度特征进行的研究,以及对不分车道行驶和分车道行驶两种情况下的车辆运行状况进行的有效仿真,可为当前公交优先通行提供较好的理论基础.     

分布式网络控制系统的输出反馈控制

建立了同时具有前向通道传输时延和反馈通道传输时延的线性分布式网络控制系统的数学模型.用该数学模型将系统变换为具有状态与控制时变时滞的线性时滞系统.基于代数Riccati方程方法,提出了H∞鲁棒输出反馈控制方法,以使系统闭环控制稳定.仿真算例结果表明,在t=2.5 s时,系统状态都达到了0,保证了系统具有较快的零状态响应速度.给出了这类系统的H∞鲁棒输出反馈控制器的综合设计示例.     

一种优化的分布式光网络的动态带宽分配算法

在分析了EPON的拓扑结构及其调度机制的基础上,根据分布式计算的特点,提出了一种优化的可适用于分布式光网络的动态带宽分配算法CPDBA.该算法根据分布式计算任务的实时性和时序性,进行动态调度,并利用数据包的相关性,进行预测动态分配信用带宽.该算法能适用于分布式光网络,并减少了数据包的时延.     

A methodology for identifying similar days in air traffic flow management initiative planning

This article describes a methodology for selecting days that are comparable in terms of the conditions faced during air traffic flow management initiative planning. This methodology includes the use of specific data sources, specific features of calendar days defined using these data sources, and the application of a specific form of classification and then cluster analysis. The application of this methodology will produce results that enable historical analysis of the use of initiatives and evaluation of the relative success of different courses of action. Several challenges are overcome here including the need to identify the appropriate machine learning algorithms to apply, to quantify the differences between calendar days, to select features describing days, to obtain appropriate raw data, and to evaluate results in a meaningful way. These challenges are overcome via a review of relevant literature, the identification and trial of several useful models and data sets, and careful application of methods. For example, the cluster analysis that ultimately selects sets of similar days uses a distance metric based on variable importance measures from a separate classification model of observed initiatives. The methodology defined here is applied to the New York area, although it could be applied by other researchers to other areas.     

Modification of the Highway Capacity Manual two‐lane highway analysis procedure for Spanish conditions

The US Highway Capacity Manual (HCM) methodology is used in Spain to evaluate traffic operation and quality of service. The effect of passing manoeuvre on two‐lane highway operational performance is considered through adjustment factors to average travel speeds and percent time spent following. The procedure is largely based on simulations in TWOPAS and passing behaviours observed during US calibrations in the 1970s. It is not clear whether US driving behaviour and vehicles' performance are comparable with Spanish conditions. The objective of this research is to adapt the HCM 2010 methodology to Spanish driver behaviour, for base conditions (i.e. no passing restrictions). To do so, TWOPAS was calibrated and validated based on current Spanish passing field data. The calibration used a genetic algorithm. The case study included an ideal two‐lane highway with varying directional traffic flow rate, directional split and percentage of trucks. The updated methodology for base conditions is simpler than the current HCM 2010 and does not rely on interpolation from tables. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling delay at signalized intersections with channelized right‐turn lanes considering the impact of blockage

This paper presents a probabilistic delay model for signalized intersections with right‐turn channelization lanes considering the possibility of blockage. Right‐turn channelization is used to improve the capacity and to reduce delay at busy intersections with a lot of right‐turns. However, under heavy traffic conditions the through vehicles will likely block the channelization entrance that accrues delay to right‐turn vehicles. If the right‐turn channelization gets blocked frequently, its advantage in reducing the intersection delay is neglected and as a result the channelization lane becomes inefficient and redundant. The Highway Capacity Manual (HCM) neglects the blockage effect, which may be a reason for low efficiency during peak hours. More importantly, using HCM or other standard traffic control methods without considering the blockage effects would lead to underestimation of the delay. To overcome this issue, the authors proposed delay models by taking into account both deterministic and random aspects of vehicles arrival patterns at signalized intersections. The proposed delay model was validated through VISSIM, a microscopic simulation model. The results showed that the proposed model is very precise and accurately estimates the delay. In addition, it was found that the length of short‐lane section and proportion of right‐turn and through traffic significantly influence the approach delay. For operational purposes, the authors provided a step‐by‐step delay calculation process and presented approach delay estimates for different sets of traffic volumes, signal settings, and short‐lane section lengths. The delay estimates would be useful in evaluating adequacy of the current lengths, identifying the options of extending the short‐lane section length, or changing signal timing to reduce the likelihood of blockage. Copyright © 2016 John Wiley & Sons, Ltd.     

An exact modelling of the uniform control traffic delay in undersaturated signalized intersections

The average delay experienced by vehicles at a signalized intersection defines the level of service (LOS) at which the intersection operates. A major challenge in this regard is the ability to accurately estimate all the components underlying the overall control delay, including the uniform, incremental and initial queue delays. This paper tackles this challenging task by proposing a novel exact model of the uniform control delay component with a view to enhancing the accuracy of the existing approximate models, notably, the one reported in the Highway Capacity Manual 2010. Both graphical and analytical proofs are employed to derive exact closed‐form expressions for the uniform control delay at undersaturated signalized intersections. The high degree of accuracy of the proposed models is analysed through extensive simulations to demonstrate their abilities to exactly characterize the performance of real‐life intersections in terms of the resulting vehicle delay. Unlike the existing widely adopted uniform delay models, which tend to overestimate the LOS of real‐life intersections, the delay models introduced in this paper have the merit of exactly capturing such a LOS. Copyright © 2016 John Wiley & Sons, Ltd.     

基于行人的信号交叉口右转车控制条件

针对保障行人过街道舒适性和安全性的信号控制问题,考虑行人的过街需求,分右转车与两进口行人完全分离、特定时间段右转控制两种条件,建立信号控制延误和行人干扰延误的分析模型,进而提出相应的右转车辆控制条件。以一四相位十字形信号交叉口为研究对象,采用与左转相位相同和进口人行道绿灯相位禁行两种控制方式进行应用仿真,结果表明,在右转车流量一定时,右转车不受控制时延误与行人流量成正比,当行人流量达到1 000人/h、右转车流量达到400 veh/h时,右转车延误超过C级服务水平延误值的上限;实施控制后,右转车延误随流量的增加而递增,与行人流量无关,且第2种控制方式下的延误更小。