Estimation of multinomial probit-kernel integrated choice and latent variable model: comparison on one sequential and two simultaneous approaches

Integrated choice and latent variable (ICLV) model incorporates latent factors into standard discrete choice model with aim to provide greater explanatory power. Using simulated datasets, this study makes a comparison among three estimation approaches corresponding to the sequential approach and two simultaneous approaches including the maximum simulated likelihood with GHK estimator and maximum approximate composite marginal likelihood (MACML) approach, to evaluate their abilities to recover the underlying parameters of multinomial probit-kernel ICLV model. The results show that both simultaneous approaches outperform the sequential approach in terms of estimates accuracy and efficiency irrespective of the sample sizes, and the MACML approach is the most preferable due to its best performance on recovering true values of parameters with relatively small standard errors, especially when the sample size is large enough.     

Household structure and gender differences in travel time: spouse/partner presence,parenthood, and breadwinner status

Despite having more similar roles at work and home than ever before, US men and women continue to exhibit different travel behavior. An open question is whether the remaining gender differences in travel differ by traditional and emergent aspects of household structure such as spouse/partner presence, parenthood, and breadwinner status. Using data from the 2003–2010 American Time Use Survey, this study offers a unique, empirical travel time analysis of metropolitan workers stratified by household structure. Results show that gender differences in travel time respond to multiple aspects of household structure in complex and interactive ways. Gender difference in work travel time is only observable when spouse/partner presence and parenthood interact, i.e., in couple households with children. Gender difference in household support travel reacts to parenthood but not spouse/partner presence. Gender difference in travel time between employed females and employed males in single-breadwinner couples is no different from gender difference in double-breadwinner couples. The results call for policy initiatives and research inquiries that pay greater attention to the large gender disparities in work travel in couple households with children and the large gender disparities in household support travel in all households with children including single-parent households. Although incapable of ruling out the influences of internalized gender differences (e.g., preference theory) and gendered structural contexts (e.g., labor market segmentation), the findings provide clear evidence that traditional gender roles and relations remain operative in contemporary households in the US.     

The interactions between online shopping and personal activity travel behavior: an analysis with a GPS-based activity travel diary

Accompanying the widespread use of the Internet, the popularity of e-commerce is growing in developing countries such as China. Online shopping has significant effects on in-store shopping and on other personal activity travel behavior such as leisure activities and trip chaining behavior. Using data collected from a GPS-based activity travel diary in the Shangdi area of Beijing, this paper investigates the relationships between online shopping, in-store shopping and other dimensions of activity travel behavior using a structural equation modelling framework. Our results show that online buying frequency has positive effects on the frequencies of both in-store shopping and online searching, and in-store shopping frequency positively affects the frequency of online searching. Frequent online purchasers tend to shop in stores on weekends rather than weekdays. We also found a negative effect of online buying on the frequency of leisure activities, indicating that online shopping may reduce out-of-home leisure trips.     

About attitudes and perceptions: finding the proper way to consider latent variables in discrete choice models

We provide an in-depth theoretical discussion about the differences between individual-specific latent constructs (representing attitudes, for example, but also other characteristics such as values or personality traits) and alternative-specific latent constructs (that may represent perceptions) affecting the choice-making process of individuals; we also carry out an empirical exercise to analyze their effects. This discussion is of importance, as the majority of papers considering attitudinal latent variables just take these as attributes affecting directly the utility of a certain alternative, while systematic taste variations are rarely considered and perceptions are mostly ignored. The results of our case study show that perceptions may indeed affect the decision making process and that they are able to capture a significant part of the variability that is normally explained by alternative specific constants. Furthermore, our results indicate that attitudes may be a reason for systematic taste variations, and that a proper categorization of latent variables, in accordance with underlying theory, may outperform the customary assumption of linearity.     

Car today,gone tomorrow: The ephemeral car in low-income,immigrant and minority families

Most transportation research in the United States uses cross-sectional, “snapshot” data to understand levels of car access. Might this cross-sectional approach mask considerable variation over time and within households? We use a panel dataset, the Panel Study of Income Dynamics (PSID), for the years 1999–2011 to test this question. We find that for most families, being “carless” is a temporary condition. While 13 % of families in the US are carless in any given year, only 5 % of families are carless for all seven waves of data we examine in the PSID. We also find that poor families, immigrants, and people of color (particularly, blacks) are considerably more likely to transition into and out car ownership frequently and are less likely to have a car in any survey year than are non-poor families, the US-born, and whites.     

Predictors of car use habit strength in an urban Norwegian public

Car use in urban areas carries well known risks for negative effects on urban quality of life, the environment and land use. Previous psychological work has mainly studied the habit of using a car as a predictor variable, whereas only a few studies have focused on psychological factors that may underlie and shape the habit. The aim of the present study is to examine demographic characteristics, spatial variables and social–psychological factors associated with car habit use strength. The results are based on a survey conducted in a random urban population-based sample with car access recruited from the Norwegian population registry (n = 878). Car use habit strength was stronger among male than female respondents and tended to be weak with a lower income. Multivariate logistic regression showed that reporting pro-environmental attitudes and personal norms predicted a weak car use habit strength, while reporting strong priority of flexibility and a long distance from home to work predicted a strong car use habit strength. Car use habit is influenced by multiple demographic, spatial and social–psychological factors, which should be carefully addressed in interventions aimed at reducing the likelihood of developing a strong car habit strength.     

A review of guidelines for including wider economic impacts in transport appraisal

In this paper we examine how 23 industrialised countries treat wider economic impacts (WEIs) in transport appraisals. We identify 12 different types of impacts based on these countries’ appraisal guidelines. Agglomeration impacts and Production changes in imperfect markets are the most widely accepted, being recognised by 14 and 10 countries, respectively. However, about half of the impacts are mentioned by only one country, and few recommend including the impacts directly in cost–benefit analyses. Several countries provide provisos or criteria that must be met before WEIs can be assessed in the first place. We found method recommendations for quantifying WEIs in 10 countries. However, with the exception of the UK Department for Transport’s (DfT) methodological framework, there is very little international consensus on the choice of appropriate methods. Our findings thus supplement and reinforce the conclusions from the Norwegian Official Report of the Hagen Committee [NOU 2012:16. (2012). Samfunnsøkonomiske analyser. Oslo: Departementenes servicesenter] that there is currently no established consensus on the magnitude and relevance of WEIs, or on how and which of these impacts should be taken into account in transport appraisals. Recommendations for further research and appraisal practices are provided.     

PHP+MySQL环境下论坛的搭建

“PHP”论坛包括登录、注册和帖子归类等相关功能,以PHP MySQL来搭建个人论坛,整个安装过程均简单易懂。本文从PHP配置、MySQL安装、GD库安装和phpMyAdmin等五个方面介绍了安装设置过程,经过测试,该论坛达到预期目标并运行正常。     

舰船装备健康状态评估及其应用研究

文章分析了装备健康状态评估的国内外研究现状,对装备健康状态及其与技术状态之间的关系进行了较为深入的探讨,明确了舰船装备健康状态与技术状态之间的区别和联系,以及利用健康状态和技术状态进行装备状态评估的优缺点。最后根据舰船装备的实际需求,将舰船健康状态的概念引入到舰船的使用和维修过程中,提出了健康状态在舰船使用、维修和训练方面的应用设想。     

金属基复合材料热机械疲劳寿命影响参数研究

基于细观损伤机理,通过对金属基复合材料在热/机械循环载荷下疲劳破坏的数值模拟,研究了六种参数对疲劳寿命的影响.结果表明:(1)疲劳寿命随着试样尺寸的增大而缩短,但达到临界尺寸,即纤维规模超过25根或者长度超过30倍纤维直径后,疲劳寿命将不受尺寸变化的影响;(2)纤维体积含量影响了材料抗疲劳破坏的能力,疲劳寿命随着纤维体积百分含量的提高而延长;(3)疲劳寿命依赖于纤维强度Weibull分布中形状参数的变化,疲劳寿命随着形状参数的增大而延长;(4)疲劳寿命随着疲劳延性系数的增大而延长,但随着疲劳延性指数绝对值的增大而缩短.