基于灰色模糊数的公交线网优化研究

在考虑信息不完全的情况下,用灰色模糊数对公交线网优化问题进行了研究。在给出了公交线网优化的约束条件与优化目标的基础上,利用灰色模糊数建立了公交线网优化的决策模型。灰色模糊数是用三参数区间参与优化过程,在允许参数在一定范围内变化的情况下,计算后得到的结果是一个区间向量,其中向量值最大的为所求结果,适用于城市公交线网的优化问题。实例应用分析表明,优化后的公交线网效率提高,可达性良好,可满足城市公交可持续发展的要求。     

三参数区间数研究及其在决策分析中的应用

在定义三参数区间数的基础上,给出了三参数区间数的运算关系;然后将权重为区间数的多指标决 策问题转化为指标取值为三参数区间数的多指标决策问题;在三参数区间数理想方案点定义的基础上,给出了 权重为三参数区间数的逼近理想点法;最后将其应用于某城市公交线网的优化调整中。结果表明,该法科学合 理、切实可行。     

基于物元矩阵的多指标理想决策法

针对权重未知的多指标决策问题,利用物元矩阵和理想点法进行了研究．在自定义方案指标矩阵、方案标准指标矩阵、正理想方案指标矩阵和负理想方案指标矩阵等的基础上,依据决策方案到正负理想方案指标矩阵距离大小,建立了决策模型,并给出了模型的求解过程．依据极值原理,利用拉格朗日函数得到各个指标的权重值．实例应用表明,基于物元矩阵的理想决策模型,计算过程简单、实用性强、具有广泛推广价值．     

Measuring speed consistency for freeway diverge areas using factor analysis

Although either absolute speed or speed difference can be considered as a measure for speed consistency, few researches consider both in practice. The factor analysis method was introduced to extract an optimal number of factors from numerous original measures. The freeway diverging zone was divided into four elements, namely the upstream, the diverge area, the downstream and the exit ramp. Operating speeds together with individual vehicle speeds were collected at each element with radar guns. Following the factor analysis procedure, two factors, which explain 96.722% of the variance in the original data, were retained from the initial seven speed measures. According to the loadings after Varimax rotation, the two factors are clearly classified into two categories. The first category is named "speed scale" reflecting the absolute speed, and the other one is named "speed dispersion" interpreting speed discreteness. Then, the weighted score of speed consistency for each diverge area is given in terms of linear combination of the two retained factors. To facilitate the level classification of speed consistency, the weighted scores are normalized in the range of (0, 1.0). The criterion for speed consistency classification is given as 0≤F N <0.30, good consistency; 0.30≤F N <0.60, fair consistency; 0.60≤ F N ≤1.00, poor consistency. The validation by comparing with previously developed measures shows that the proposed measure is acceptable in evaluating speed consistency.