CO2 emissions: Are land-use changes enough for California to reduce VMT? Specification of a two-part model with instrumental variables

With vehicle miles of travel increasing at a faster pace than population, one strategy being actively pursued by both state and local governments is compact development. California recently passed legislation that aggressively promotes sustainability by endorsing and rewarding compact development. Likewise, the California Air Resources Board has set a statewide reduction target of 5MMT of greenhouse gas reductions from land use, based largely on achieving compact development patterns. In this paper, we use a multivariate two-part model with instrumental variables, which corrects for residential location self-selection bias. We use a much larger and more geographically representative travel survey on household travel patterns and socio-economic characteristics than represented in previous California studies; this allows us to robustly consider other influences on travel. Our results indicate that, all else equal, a 10% in residential density would reduce VMT by 1.9%. This elasticity is larger than the reported in previous econometric studies for the US, and specifically for California. However, as we show, the magnitude of this impact is still low considering reasonable ranges for policies aimed to increase residential density.     

Separation of car-dependent commuters from normal-choice riders in mode-choice analysis

The ever-increasing use of cars is a big problem in metropolitan areas. To manage the traffic stream and alleviate air pollution, most metropolitan governments are attempting to discourage the use of cars. Nevertheless, the results have not been satisfactory. It is well known that normal-choice riders choose their travel mode based on utility, which is determined by mode-specific impedances and individual characteristics. On the other hand, this study focuses on identifying car-dependent commuters who tend to keep driving cars regardless of the circumstances they are confronted with. For this study, psychometric factors characterizing car-dependent commuters were investigated. However, the performance of the mode-choice model was not sufficiently enhanced despite incorporation of the psychometric factors. The performance improved considerably when the car-dependent commuters were excluded. Based on psychometric factors, the support vector machine successfully separated the car-dependent commuters from normal-choice riders.

基于S/P值的道路隧道照明光源光谱及相关色温研究

为解决选取隧道照明光源时未考虑光谱能量分布和相关色温因素造成光源选用不当的问题,结合中间视觉模型,对道路隧道常用光源的光谱能量分布和相关色温进行测试研究,分析不同隧道常用光源的光谱能量分布与相关色温关系; 通过引入光谱S/P值的计算方法,从人眼感知角度分析不同隧道常用光源S/P值与相关色温关系。研究表明： 1）LED光源的相关色温随着蓝光比例的增加而增加; 2）不同类型光源的S/P值与光源的相关色温不是一一对应的关系,但LED光源的S/P值随着相关色温的增加而增大; 3）金属卤化物灯、白色荧光灯和LED光源适合应用于隧道照明,但从长远来看,隧道照明选用相关色温较高的LED光源更为合理。     

Urban spatial location advantage: The dual of the transportation problem and its implications for land-use and transport planning

Numerous recent studies have investigated the relationship between the location of jobs and housing in urban areas and how this relates to urban commuting patterns. Few have utilised the dual of the transportation problem of linear programming (TPLP) to provide insights into these relationships Accordingly, this analysis utilises the TPLP to determine dual variable values (shadow prices) for a study area in Dublin, Ireland. The approach determines the pattern of relative location advantage for the peak and off-peak travel periods and for public and private transport for 1991 and 2001. The results are set against the expected results for hypothetical urban structures. The results show that the pattern of relative location advantage has altered sharply over the study period for off-peak trip-making but has remained more or less the same for trip-making in the peak period. For the off-peak period, the pattern of relative location advantage has shifted from the central area to the periphery specifically for private transport trips; for public transport, the pattern has remained focused on the city centre. This indicates that private transport users can react more quickly to changes in the distribution of land-use activities than their public transport counterparts due to the relatively fixed nature of the latter mode. This implies that the public transport network needs to be reorganized to better reflect the revised pattern of trip-making specifically for the off-peak period. The results demonstrate the value of using the approach for providing information about the spatial organisation of land uses within cities and where future development may be targeted.     

基于Authorware的计算器的实现

分析了利用Authorware强大功能的系统函数结合变量,开发出优秀的交互多媒体作品,讨论了使用这些函数和变量编写计算器应用软件的方法,并给出了开发的流程及其具体的实现.     

直墙式防波堤的可靠度分析

为探讨独立或相关荷载变量对结构可靠指标β值的影响,利用广义随机空间极限状态曲面上任一点处切平面法线确定可靠指标,在变量相关情况下采用改进的JC法或推导的HL法,对一座直墙堤实例进行核算,表明可靠指标符合良好,荷载相关时的可靠指标明显低于假定荷载独立时的结果。     

船体梁抗弯能力的计算

在船舶纵弯曲强度的可靠性分析中,需要计算船体梁的抗弯能力,本文提供一种实用计算方法。在此方法中取材料厚度(或剖面积)和屈服限、弹性模量等均为随机变量,利用随机函数的线性化原理,求得船体断面几何要素以及抗弯能力的统计特征值。文中还介绍了国产船用钢材的厚度和屈服极限的变异系数,并利用组合梁模型试验资料对采用梁模型带来的计算误差及其修正办法作了讨论。该计算方法采用了造船人员熟悉的常规强度计算中的格式,便于在船舶设计中应用。     

基于灰色关联的城市轨道网络列车运行计划综合评价

城市轨道交通网络列车运行计划的综合评价不仅需衡量各条线路列车运行质量,还应着重考虑各线间列车运行接续质量。本文首先从服务质量、线间协调、首末班车协调、高峰期站台客流饱和、抗干扰性以及技术性6个方面构建城市轨道网络列车运行计划综合评价的指标体系;其次在分别采用层次分析法与熵值法确定各评价指标主观与客观权重的基础上,通过线性组合主观与客观权重而获得各评价指标权重,进而通过计算灰色关联系数确定各评价方案的灰色关联度来实现路网列车运行计划方案选优。     

A stochastic quarter-car model for dynamic analysis of vehicles with uncertain parameters

A quarter-car model is used to investigate the vibration response of cars with uncertainty under random road input excitations in this paper. The sprung mass, unsprung mass, suspension damping, suspension stiffness, and tyre stiffness are considered as random variables. The road irregularity is considered a Gaussian random process and modelled by means of a simple exponential power spectral density. The power spectral density, mean value, standard deviation, and variation coefficient of the vehicle's natural frequencies and mode shapes are obtained by using the Monte Carlo simulation method. The computational expressions for the numerical characteristics of the mean square value of the vehicle's random response in the frequency domain are developed by means of the random variable's functional moment method. The influences of the randomness of the vehicle's parameters on the vehicle's dynamic response are investigated in detail using a practical example, and some useful conclusions are obtained.     

城市交通出行行为中的潜变量研究综述

潜变量是提高交通出行行为预测精度的有效方法,潜变量的提出为出行行为 研究提供了新视角.为解决目前出行行为中缺少潜变量概念认知及潜变量应用的问题,本 文从社会心理学入手,分析已有出行行为建模方法的特点,提出潜变量研究的必要性,对 出行行为中潜变量内涵、应用领域、模型构建进行系统梳理,明确潜变量研究的三个核心 问题是识别、有效性验证及计算.评述与研究涵盖潜变量的出行行为整合模型的机遇、难 点和挑战.并揭示潜变量测度方法与SP/RP 调查的关联性,综述潜变量模型检验判定标 准,最后总结出行行为潜变量研究的发展趋势及发展方向.