改扩建公路超高设计中若干问题的探讨

超高设计是道路曲线路段的重要设计内容,也是行车安全性和舒适性的重要影响因素,在高等级公路改扩建应用中尤为重要。基于S226省道温岭岙环至玉环龙溪段拓宽改造项目,结合JTG D20—2017《公路路线设计规范》道路超高设计的相关规定,针对改扩建公路中分离式路基超高线形设计方法、S型曲线超高设置、曲线内构造物超高验算以及老路路拱过渡等特殊超高问题,提出新老路间的差异平稳过渡方案,借以探讨改扩建公路超高设计的思路和方法。     

基于S-曲线的时变交通应急疏散需求预测

总结了当前国内外突发公共事件应急交通疏散需求预测的研究现状.结合运筹学中的相关理论,建立了用于分析应急交通资源优化配置的避难场所定位模型,以及预测应急交通需求分布的运输问题数学模型,以确定人员运输需求量分布OD矩阵和物资运输需求量分布OD矩阵.提出了一个改进的应急交通需求时变曲线函数.以重庆天原化工总厂的氯气泄漏事件为研究对象,选取TransCAD作为仿真平台,确定事件影响范围内需要紧急撤离的人员运输需求的静态OD矩阵,根据应急交通需求时变曲线函数获得时变的宏观交通需求信息.     

Airline competition and market frequency: A comparison of the s-curve and schedule delay models

We compare two common ways of incorporating service frequency into models of airline competition. One is based on the so called s-curve, in which, all else equal, market shares are determined by frequency shares. The other is based on schedule delay—the time difference between when travelers wish to travel and when flights are available. We develop competition models that differ only with regard to which of the above approaches is used to capture the effect of frequency. The demand side of both models is an approximation of a nested logit model which yields endogenous travel demand by including not traveling in the choice set. We find symmetric competitive equilibrium for both models analytically, and compare their predictions concerning market frequency with empirical evidence. In contrast to the s-curve model, the schedule delay model depicts a more plausible relationship between market share and frequency share and accurately predicts observed patterns of supply side behavior. Moreover, the predictions from both models are largely the same if we employ numerical versions of the model that capture real-world aspects of competition. We also find that, for either model, the relationship between airline frequency and market traffic is the same whether frequency is determined by competitive equilibrium, social optimality, or social optimality with a break-even constraint.     

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本文着重研究应急交通需求时空分布预测方法. 从分析应急交通需求特点入手,在总结现有研究的基础上,提出广义S型行为反应曲线的概念,并紧扣不同集结点的疏散时间要求和反应参数各异的特点,建立了广义S型需求加载曲线模型,同时给出了单位时段疏散百分比的分析方法. 应用上述方法,设计了分时段应急交通OD需求矩阵的求解算法,从而建立应急交通需求时空分布模型. 基于MATLAB软件对模型编程实现,在对给定算例进行应用后,证明模型能够准确刻画不同时刻的各集结点和整个系统的应急需求疏散比例的动态变化,并有效应用于应急交通时变需求分布的预测.