Accommodating risk in the valuation of expected travel time savings

Valuation of travel time savings is a critical measure in transport infrastructure appraisal, traffic modelling and network performance. It has been recognised for some time that the travel times associated with repeated trips are subject to variation, and hence there is risk embedded in the treatment of expected travel time. In the context of the expected utility framework, we use a nonlinear probability weighting function to accommodate choice made under risk. Although the empirical findings suggest small differences between the value of expected travel time savings (VETTS) in the presence and absence of risk, the mean estimate does make a noticeable difference to time benefits when applied to real projects. By incorporating nonlinear probability weighting, our model reveals that the probabilities associated with specific travel times that are shown to respondents in the choice experiment are transformed, resulting in overweighting of outcomes with low probabilities and underweighting of outcomes with high probabilities. Copyright © 2011 John Wiley & Sons, Ltd.     

拍戏

受金融海啸的影响,比赛赞助费用降低,我只能减少今年比赛的场次;同时公司也没有太多工作让我做。因此除了比赛和平时上班,多出很多业余时间。因为以前比赛繁忙时间有冲突不得不拒绝的一些媒体采访,这下有了充分空闲来做。跟媒体打交道,是车手职责的一部分。     

去英国买头盔——How to Buya Helmet

前年我第一次参加澳门大赛车时,为了这个特殊而荣耀的第一次,我从日本订了一个新头盔。但新头盔戴上之后却发现太紧了,跟孙悟空被唐僧念了紧箍咒一样头痛欲裂,无奈弃置不用。新赛季即将开始,旧头盔就要过期,我必须要更换新头盔,于是我踏上英国之旅。     

谁对谁错——Who Is Correct？

赛车的每一场比赛都是一场赌博。车手做了最好的准备,车队夜以继日地工作,在现有条件下努力打造赛车,但最后获得的,可能只是个教训。但是赛车运动的魅力也在此,有时候不管你扔进去多少钱,但结果并不会按照个人意愿顺利实现。     

The impact of a port on its local economy: the case of Plymouth

It has been suggested in two potentially influential documents that the development of ports could be an important tool of regional economic growth in areas such as South West England. This proposition is analysed in this article by detailed examination of the case of Plymouth, one of the areas in the region for which port development has been mooted. It is concluded that the Plymouth evidence suggests that it is easy to exaggerate the existing and potential role of ports in the regional development process. Ports are not big employers of labour and are no longer the inter-related industrial complexes that they once were. In most cases, therefore, they serve industry in areas distant from their own.     

Marine Protected Area Management Effectiveness: Progress and Lessons in the Philippines

Quantifying progress in management of marine protected areas (MPAs) is crucial to marine conservation and fisheries management in the Philippines. This study compiles data on the status, occurrence, and management gaps of MPAs through coordination with multiple organizations supporting and guiding MPAs in the Philippines. MPA management effectiveness was measured using a MPA Rating System. Since 2002 the modal MPA rating levels increased from level 1 (initiated) to level 4 (sustained) in 2008/9. This upward trend is attributed to factors that promoted both the establishment and improved management of MPAs. Analysis indicated that: (1) most MPAs struggle with budgetary constraints or lack of sustainable financing and (2) overall the MPAs are being maintained and progressing with notable improvement in management despite a range of difficulties encountered during the implementation process. For MPAs in the Visayan Region for which biophysical data were available, the MPA Rating System was used to assess the effectiveness of local government capacity building on MPA coral reef health. Our results suggest that MPAs with higher ratings are likely to have better reef health conditions.     

Inferring attribute non-attendance from stated choice data: implications for willingness to pay estimates and a warning for stated choice experiment design

There is a growing interest in traveller behaviour research to explore alternative information processing strategies (often referred to as heuristics or rules) adopted by individuals when assessing packages of attributes describing alternatives in a choice set, and making a choice. One popular attribute processing rule relates to attributes not being considered (i.e., being ignored), for all manner of reasons, referred to in the small but growing literature as attribute non-attendance or non-preservation. Researchers have used a mixture of methods to study the role of attribute non-attendance, including supplementary questions on whether each attribute is ignored or not, and methods in which the functional form of the utility expressions defining an alternative can recognise the possibility, up to a probability, of an attribute being ignored. Although supplementary questions are worthy of further consideration, despite the controversy as to the reliability of the response, recent interest has focused on ways to establish the incidence of attribute non-attendance without recourse to such evidence. In this paper we use an existing data set of choice amongst four attributes describing alternative car non-commuting trips, to illustrate the proposed method, and to compare values of travel time savings under each possible combination of non-attendance attributes relative to a model in which all attributes are assumed to be fully attended to. The paper reveals a major concern with the way that attribute levels and ranges are selected in the design of choice experiments, which can induce non-attendance situations where willingness to pay estimates cannot be obtained.     

Can scale and coefficient heterogeneity be separated in random coefficients models?

There is growing interest in the notion that a significant component of the heterogeneity retrieved in random coefficients models may actually relate to variations in absolute sensitivities, a phenomenon referred to as scale heterogeneity. As a result, a number of authors have tried to explicitly model such scale heterogeneity, which is shared across coefficients, and separate it from heterogeneity in individual coefficients. This direction of work has in part motivated the development of specialised modelling tools such as the G-MNL model. While not disagreeing with the notion that scale heterogeneity across respondents exists, this paper argues that attempts in the literature to disentangle scale heterogeneity from heterogeneity in individual coefficients in discrete choice models are misguided. In particular, we show how the various model specifications can in fact simply be seen as different parameterisations, and that any gains in fit obtained in random scale models are the result of using more flexible distributions, rather than an ability to capture scale heterogeneity. We illustrate our arguments through an empirical example and show how the conclusions from past work are based on misinterpretations of model results.     

升级

因为两场比赛撞期,我错过了上一场的香港房车锦标赛。这次没有撞期,却在比赛开始前突然被告知我不可以参加N组赛事。由于情况发生突然,没有足够时间寻找配件升级改装赛车,我只好驾驶N组赛车参加高手云集的A组比赛。     

Accommodating perceptual conditioning in the valuation of expected travel time savings for cars and public transport

Travel time variability (i.e., random variations in travel time) leads to a travel time distribution for a repeated trip from a fixed origin to destination (e.g., from home to work). To represent travel time variability, a series of possible travel times per alternative (departure time, route or mode) are often used in stated choice experiments. In the traditional models, the probabilities associated with different travel scenarios (e.g., arriving early, on time and late) shown in the experiments are directly used as weights. However, evidence from psychology suggests that the shown probabilities may be transformed (underweighted or overweighted) by respondents. To account for this transformation of probabilities, this study incorporates perceptual conditioning through a non-linear probability weighting function into a utility maximisation framework, within which the empirical estimate of the value of expected travel time savings is estimated. The key advantage of this framework is that the estimated willingness to pay value can be directly linked to the source of utility (i.e., the probability distribution of travel time), while taking into account the perceptual transformation of probabilities.