Catching the tail: Empirical identification of the distribution of the value of travel time

Recent methodological advances in discrete choice analysis in combination with certain stated choice experiments have allowed researchers to check empirically the identification of the distribution of latent variables such as the value of travel time (VTT). Lack of identification is likely to be common and the consequences are severe. E.g., the Danish value of time study found the 15% right tail of the VTT distribution to be unidentified, making it impossible to estimate the mean VTT without resorting to strong assumptions with equally strong impact on the resulting estimate. This paper analyses data generated from a similar choice experiment undertaken in Sweden during 2007-2008 in which the range of trade-off values between time and money was significantly increased relative to the Danish experiment. The results show that this change allowed empirical identification of effectively the entire VTT distribution. In addition to informing the design of future choice experiments, the results are also of interest as a validity test of the stated choice methodology. Failure in identifying the right tail of the VTT would have made it difficult to maintain that respondents’ behaviour is consistent with utility maximisation in the sense intended by the experimenter.     

Hazard perception test development for Lithuanian drivers

Hazard perception tests may not be transferable between different countries, due to differences in traffic culture and infrastructure. Therefore, different instruments might be necessary for assessing hazard perception in various countries. The aim of the current study was to develop the Lithuanian hazard perception test based on static traffic images and test its psychometric properties. Thirty-four experienced drivers participated in a pilot study, and 125 drivers with diverse driving experience took part in the main study. The final test contained 27 static traffic scenes and the participants were asked to respond if they saw a hazard or not. Results demonstrated that the test has satisfactory internal consistency and test-retest reliability. It differentiated between inexperienced and experienced drivers, and between those experienced drivers who had less than three or more than three crashes in their driving history. The test has sufficient psychometric properties for research; still further development is needed in order to apply it for individual testing and decisions about licence provision.     

英语口语测试的信度和效度研究

英语口语测试是一项能力测试,目的是要提高学生的听说能力。在测试中,信度和效度是评估测试的两个主要标准。因此,测试的成功与否,在很大程度上取决于其信度与效度。     

上层建筑参加船体总纵弯曲程度研究

本文用有限元法及光弹性实验对某船的上层建筑与主船体之间的相互作用作了全面、详细的分析，得到各部位的各种应力分布曲线，在上层建筑的应力分析和有效性研究方面获得了许多有用的数据。在此基础上对有关上层建筑设计的某些方面进行了讨论。     

关于高速公路项目管理有效性的思考

高速公路建设规模巨大,建设周期长,管理工作十分复杂。对于项目管理者本身,需要有清楚的工作思路,不断提高管理的有效性,才能保证工程建设有序受控。笔者通过对高速公路项目指挥部管理工作实践的深入思考,从项目指挥部现场管理的角度分析管理工作特点,提出有效管理的概念和建议,供业内同行参考。