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41.
The robustness of questionnaire results to various forms of bias are explored in the context of a dual-mode (web and hardcopy)
survey of employers’ anticipations of levels of employee commuting and business travel activity under a range of future ICT
scenarios. The questionnaire incorporated several innovative features which, together with the dual-mode format, allowed an
unusually wide range of analyses. For example: the robustness of respondents’ opinions was tested by examining the effect
of incorporating alternative versions of a briefing text, one being very positive and one very negative, about the role of
ICT; instrument bias was identified via detailed comparison of the results from the two versions of the questionnaire; and
the impact of exogenous factors which are often ignored or taken as constant was assessed via special supplementary questions.
Analysis showed that the robustness of opinions and expectations varied and was influenced by respondent characteristics,
and that results from the two versions of the questionnaire differed significantly. It is concluded that opinions and expectations
are less robust, and questionnaire results are more subject to bias and myopic interpretation, than is generally recognised
and that web-based surveys seem particularly vulnerable to sampling bias. Methods are suggested for measuring robustness,
for reducing bias and for validating and contextualising results. The use of contrasting briefing texts is recommended as
a means of establishing the robustness of opinions and expectations while supplementary questions are recommended for validating
and contextualising SP and SE exercises.
Peter Bonsall Professor of Transport Planning at the Institute for Transport Studies, University of Leeds. His research interests include: use of innovative data sources, microsimulation, multi-criteria appraisal of policy interventions, travellers’ perception of modal attributes, their ability to cope with uncertainty and complexity and their response to new information and charges. Jeremy Shires Senior Research Fellow at the Institute for Transport Studies, University of Leeds. His research interests include behavioural modelling, the impact of “soft factors” on travel, stated preference design and public transport demand modelling. 相似文献
Peter BonsallEmail: |
Peter Bonsall Professor of Transport Planning at the Institute for Transport Studies, University of Leeds. His research interests include: use of innovative data sources, microsimulation, multi-criteria appraisal of policy interventions, travellers’ perception of modal attributes, their ability to cope with uncertainty and complexity and their response to new information and charges. Jeremy Shires Senior Research Fellow at the Institute for Transport Studies, University of Leeds. His research interests include behavioural modelling, the impact of “soft factors” on travel, stated preference design and public transport demand modelling. 相似文献
42.
Lidia P. Kostyniuk 《Transportation》2009,36(6):641-642
43.
Borja Beltran Stefano Carrese Ernesto Cipriani Marco Petrelli 《Transportation Research Part C: Emerging Technologies》2009,17(5):475-483
The use of fossil fuels in transportation generates harmful emissions that accounts for nearly half of the total pollutants in urban areas. Dealing with this issue, local authorities are dedicating specific efforts to seize the opportunity offered by new fuels and technological innovations in achieving a cleaner urban mobility. In fact, authorities are improving environmental performances of their public transport fleet by procuring cleaner vehicles, usually called low and zero emission vehicles (LEV and ZEV, respectively). Nevertheless there seems to be a lack of methodologies for supporting stakeholders in decisions related to the introduction of green vehicles, whose allocation should be performed since the network design process in order to optimize their available green capacity.In this paper, the problem of clean vehicle allocation in an existing public fleet is faced by introducing a method for solving the transit network design problem in a multimodal, demand elastic urban context dealing with the impacts deriving from transportation emissions.The solving procedure consists of a set of heuristics which includes a routine for route generation and a genetic algorithm for finding a sub-optimal set of routes with the associated frequencies. 相似文献
44.
Julie Paquette François Bellavance Jean-François Cordeau Gilbert Laporte 《Transportation》2012,39(3):539-564
In many countries, dial-a-ride services are provided by public authorities to elderly and handicapped people who cannot use
regular transit. Cost minimization is key to running these services, but one can observe a growing interest in quality measurement
and improvement. A first step in improving quality is to define a quality measurement scale specific to dial-a-ride services.
A second step is to incorporate quality measurements in mathematical models that serve as a basis for optimization algorithms.
To this end, an extensive survey of dial-a-ride users was conducted in Longueuil, the largest suburb of Montreal, Canada.
This paper describes the steps of the survey and presents its main conclusions: (1) 56 attributes were identified based on
interviews, (2) the questionnaire developed has proved to be reliable and valid, (3) an exploratory factor analysis allowed
us to determine 13 dimensions of quality in dial-a-ride services, (4) the most important criteria for users were identified,
and (5) population segmenting variables by which subgroups of users can be categorized were also determined. Managerial implications
of our results are also discussed. 相似文献
45.
Guro Persdotter Fjeld Sturle Danielsen Tvedt Helle Oltedal 《WMU Journal of Maritime Affairs》2018,17(4):475-495
The present review examines the research literature on Non-Technical Skills (NTS) used by ships’ bridge officers in connection with navigation. The aim of the study was to (i) identify the cognitive and interpersonal skills which have been the focus of previous studies and (ii) explore how the content of these skills has been described. Databases searched included Academic Search Premier, PsycINFO, Science Direct, and Web of Science. Nineteen studies were included in the review. Five NTS were identified: situation awareness (SA), decision-making (DM), workload management (WM), communication, and leadership. In addition to discussing each skill, the review raises four overarching issues with the present literature for the bridge domain: (1) Have all the relevant skills been subject to exploration? (2) Have the skills identified been explored in detail? (3) There seems to be an uneven distribution of research between cognitive and interpersonal skills. (4) There is little research into understanding the skills as a complete taxonomy. Knowledge on how the skills are linked and interplay with one another is incomplete. Overall, further research on all these aspects of NTS in the maritime domain could increase scientific understanding and contribute to bridge operational practice and to the further development and evaluation of NTS training such as Bridge Resource Management (BRM). 相似文献
46.
47.
Seyed Masoud Mahmoudof Peyman Badiei Seyed Mostafa Siadatmousavi Vahid Chegini 《船舶与海洋工程学报》2018,17(1):140-151
This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version 41.01) in predicting significant wave height and spectral peak energy content for swell waves in very shallow water of surf zone during depth-induced wave breaking and dissipation. The model results were compared with field measurements at five nearshore stations. The results demonstrated that some breaker index formulations were successful for significant wave height prediction in surf zones. However, an incorrect shape of the energy spectrum and overestimated near spectral peak energy content at shallow water stations were obtained using all of the embedded depth-induced wave breaking formulations in SWAN. The dependent breaker index on relative depth (Kpd) formulation, which was successful in predicting near spectral peak energy content, resulted in an average error of 30%. Finally, this formulation was modified to enhance the model performance in reproducing the spectral peak energy content. 相似文献
48.
A numerical study of ship-to-ship interaction forces is performed using a commercial CFD code, and the results are compared with experimental data and with the results of a panel method analysis. Two ship models have been used in the interaction forces analysis: a tug and a tanker, advancing parallel to each other with different lateral distances and two different values of the fluid depth. Computations are carried out with four different flow models: inviscid and viscous flow with the free surface modeled as a rigid wall and inviscid and viscous flow with the deformable free surface. A fair agreement was obtained with available experimental data and results obtained by panel method. The influence of viscosity in the computations is found to be comparatively weak, while the wavemaking effects may be important, at small magnitude of the horizontal clearance. 相似文献
49.
In this work, trapped mode frequencies are computed for a submerged horizontal circular cylinder with the hydrodynamic set-up involving an infinite depth three-layer incompressible fluid with layer-wise different densities. The impermeable cylinder is fully immersed in either the bottom layer or the upper layer. The effect of surface tension at the surface of separation is neglected. In this set-up, there exist three wave numbers: the lowest one on the free surface and the other two on the internal interfaces. For each wave number, there exist two modes for which trapped waves exist. The existence of these trapped modes is shown by numerical evidence. We investigate the variation of these trapped modes subject to change in the depth of the middle layer as well as the submergence depth. We show numerically that two-layer and single-layer results cannot be recovered in the double and single limiting cases of the density ratios tending to unity. The existence of trapped modes shows that in general, a radiation condition for the waves at infinity is insufficient for the uniqueness of the solution of the scattering problem. 相似文献
50.
In this paper, a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation. The hydrodynamic performance of a T-barge is investigated in the frequency domain, and the coupled motions are analyzed in the time domain. We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well. The barge exhibits favorable hydrodynamic behavior in the considered sea state, and the equipment loads are allowable. The mooring system and sway fender forces are within the permissible range. Based on these results, we can verify that the actual installation of the offshore platform is feasible. We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation, which is of great importance. As such, we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance. 相似文献