Mitigating environmental impacts in advance: Evidence of cost and time savings for transportation projects

The traditional model for mitigating a transportation project’s environmental impacts typically operates project-by-project and delivers the mitigation just-in-time. In contrast, the newer practice of advance mitigation comprehensively assesses and mitigates impacts from one or multiple transportation projects before or during project planning, sometimes long before project construction begins. The practice has gained adherents for its potential to improve ecological outcomes, by better aligning mitigation and conservation goals. Advance mitigation also stands to reduce mitigation costs, an important secondary benefit for transportation agencies with constrained resources. Evidence of cost savings, however, has been piecemeal and anecdotal. This paper advances knowledge of advance mitigation’s financial impacts in two ways. First, it critically assesses the evidence about cost savings realized through advance mitigation, both through avoided up-front costs and reduced project delay. Second, it directly estimates the project time savings that might accrue with advance mitigation of state highway projects in California. Overall, the balance of evidence is encouraging for transportation agencies that would introduce the practice, and general agreement exists on its financial benefits. Considering project delays related only to the environmental process, we estimate advance mitigation could reduce delivery times by 1.3–5.0 months per project. Still, we also identify factors limiting comprehensive analysis. Transportation agencies adopting advance mitigation practices into their operations could use a pilot approach that includes rigorous environmental and mitigation cost accounting; such pilots would build needed empirical evidence of advance mitigation’s financial and ecological outcomes.     

论迟延交付的概念

通过法律逻辑的基本知识,分析我国《海商法》中未引进的“汉堡规则”中关于迟延交付的另一种情况——未在合理时间内交付,以减少理解上的分歧。     

城市道路路段和交叉口阻抗函数探讨

城市道路的路阻函数是交通研究中的关键点和难点．对交通分配起着至关重要的作用。本文先对城市道路路段阻抗函数进行细致的分析，通过实际调查的数据对该函数进行了验证。对信号交叉口的路阻函数进行了比较详细的分析，提出了隐性冲突点的概念，对信号交叉口阻抗函数中添加了与流向有关的心理参数项，并进行了分析和标定。     

一种晚点地铁列车实时调整策略及其动态速控模式

针对追踪运行地铁列车群,分析晚点情况下的常规“赶点”运行调整措施的缺陷,提出在晚点列车“赶点”运行调整措施的基础上,扩充后续列车的“延赶结合”运行调整策略:在晚点发生期间“延点”运行,以提高列车群分担时段客流的合理水平并挖掘节能运行的潜力;在晚点发生之后“赶点”运行,以消除前、后列车之间的晚点传播效应。基于此策略,后车ATO系统根据“追踪间隔”与“发到间隔”的双重均衡原则,以晚点时分的动态递增为依据,实时更新ATO模式曲线,并根据列车v-t实迹曲线的时序特征,动态调整牵引末速或制动初速,避免列车v-t实迹曲线与最优ATO模式曲线冲突,实现基于最优ATO模式曲线的实时的列车速度控制。根据牵引电机有功电流、列车牵引加速度及其变化趋势的综合作用对于列车能耗的决定性影响的分析可知:在牵引电机有功电流与列车牵引加速度分别相等条件下,与“正点”运行相比较,“延点”运行的节能量能够弥补“赶点”运行的费能量,实现列车能耗的总量节省。     

A probabilistic framework for weather-based rerouting and delay estimations within an Airspace Planning model

In this paper, we develop a novel severe weather-modeling paradigm to be applied within the context of a large-scale Airspace Planning and collaborative decision-making model in order to reroute flights with respect to a specified probability threshold of encountering severe weather, subject to collision safety, airline equity, and sector workload considerations. This approach serves as an alternative to the current practice adopted by the Federal Aviation Administration (FAA) of adjusting flight routes in accordance with the guidelines specified in the National Playbook. Our innovative contributions in this paper include (a) the concept of “Probability-Nets” and the development of discretized representations of various weather phenomena that affect aviation operations; (b) the integration of readily accessible severe weather probabilities from existing weather forecast data provided by the National Weather Service; (c) the generation of flight plans that circumvent severe weather phenomena with specified probability threshold levels, and (d) a probabilistic delay assessment methodology for evaluating planned flight routes that might encounter potentially disruptive weather along its trajectory. Additionally, we conduct an economic benefit analysis using a k-means clustering mechanism in concert with our delay assessment methodology in order to evaluate delay costs and system disruptions associated with variations in probability-net refinement-based information. Computational results and insights are presented based on flight test cases derived from the Enhanced Traffic Management System data provided by the FAA and using weather scenarios derived from the Model Output Statistics forecast data provided by the National Weather Service.     

船用低压断路器长延时保护设计要点

本文介绍了作为DW框架式空气断路器的主要性能,并说明断路器长延时在低压电路控制电机设备时,选取最佳延时时间的方法,以满足电机设备的正常启动及线路过载或短路时尽快切断供电电路的要求.     

具三个年龄阶段的自食单种群系统的定性分析

讨论了两个具有三个年龄阶段的自食单种群模型,其中成年种群死亡率遵循logistic型.对于自治模型,得到了正平衡点全局渐进稳定的充分条件;在时滞模型中,得到了在一定条件下时滞将会改变系统正平衡点的稳定性,推广了已有结论.     

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针对以稳态理论为基础推导的自适应信号控制延误计算模型不能反映交叉口各进口道车流动态变化的情况,提出以定数理论为基础,考虑交叉口各进口道车流的动态变化过程,仿效延误三角形的推导模式,通过简化交叉口进口道的车流到达形式,并基于Markov特性建立了一段时间内自适应信号控制条件下的平均车辆延误计算模型。借助自适应信号控制软件系统(OPAC)作为仿真平台,以实际调查数据为例,延误模型计算结果与交通仿真结果的比较分析表明：建立的延误计算模型较稳态理论下的延误计算模型更能客观反映交叉口的车流运行状况。     

The optimization of lane assignment and signal timing at the tandem intersection with pre‐signal

This paper presents an integrated model for optimizing lane assignment and signal timing at tandem intersection, which is introduced recently. The pre‐signal is utilized in the tandem intersection to reorganize the traffic flow; hence, the vehicles, regardless of whether left‐turns or through vehicles, can be discharged in all the lanes. However, the previous work does not consider the extra traffic disruption and the associated delay caused by the additional pre‐signal. In the paper, the extra delay aroused by the coordination is incorporated in a lane assignment and signal timing optimization model, and the problem is converted into a mixed‐integer non‐linear programming. A feasible directions method is hence introduced to solve the mixed‐integer non‐linear programming. The result of the optimization shows that the performance of the tandem intersection is improved and the average delay is minimized. The comparison between the tandem and the conventional configuration is presented, and the results verify that the former shows better performance than the latter. In addition, the optimal sequence corresponding to the turning proportion and the optimal lane assignment at the upstream approach of the pre‐signal are presented. Furthermore, if the number of lanes is equal in all arms, the paper proves that the average delay will be reduced if lane assignment is proportional to the turning proportion and the vehicles with low proportion are discharged in advance. Copyright © 2013 John Wiley & Sons, Ltd.     

面向鲁棒性的高速铁路网络列车运行调整计划优化模型

针对高速铁路路网中出现区间封锁事件,考虑事件持续时间的不确定性,以列车运行时间和安全间隔时间为约束条件,引入路径选择唯一性约束保证列车运行调整计划的鲁棒性,以所有列车晚点时间之和的期望值最小为目标函数,建立高速铁路列车运行调整计划优化整数规划模型.设计基于优先级规则的启发式算法,求解原模型的可行解.运用拉格朗日松弛算法和最短路径算法求解该模型的松弛模型,得到原模型最优解的下界.根据可行解与最优解下界之间的距离,可以定量地衡量可行解的质量.结果表明,相较于CPLEX数学求解软件,算法求解效率较高;模型与算法能够有效生成鲁棒的列车运行调整计划,为调度员提供必要辅助决策信息.