Optimization of crashworthy marine structures

History shows that ferry and RoPax collisions with tankers can be devastating for human life. This paper follows up such a scenario to contribute to rational increase of safety of marine structures. Through the coupling of multi-objective structural optimization and crashworthiness analysis, a conventional tanker structure is optimized for higher collision tolerance, accounting for the change in hull mass, so that the increase in safety is efficient. Two new concepts, proposed here, are deemed necessary for the successful execution of this task: a ‘two-stage’ optimization approach, reducing the number of needed collision simulations, and a rapid collision simulation approach that utilizes coarse FE mesh and reduces calculation time. Combining the obtained results with the state-of-the-art knowledge, a new insight about crashworthy design of tanker structures is also realized.     

The development of public attitudes towards the Stockholm congestion trial

A full-scale congestion charging trial was carried out in Stockholm the first months of 2006. Almost half of respondents in a county-wide survey stated that they changed their attitudes towards congestion charges during the trial. Most of them became more positive.An analysis of media shows that the attitudinal change in media towards the trial coincides with the attitudinal change of the public. There was no dramatic change in the proportion of articles expressing a negative view. Instead, the result indicates that the increase in positive views was driven by a shift from neutral to positive articles during the trial.In order to ascertain why the public attitudes swung, we have analysed the anticipated and perceived effects of the trial. Generally, the analysis seems to indicate that improved understanding of the type and magnitude of concrete effects was not a main driving force behind the attitudinal change. Instead, it seems that the public attitude changed because personal experience gave a new understanding of the implications of the charges for the personal well-being. This would imply that trials, generally, may be a more useful tool than information in the process of implementing ‘difficult’ policy measures, such as congestion charges.     

Inter-temporal variation in the travel time and travel cost parameters of transport models

The parameters for travel time and travel cost are central in travel demand forecasting models. Since valuation of infrastructure investments requires prediction of travel demand for future evaluation years, inter-temporal variation of the travel time and travel cost parameters is a key issue in forecasting. Using two identical stated choice experiments conducted among Swedish drivers with an interval of 13 years, 1994 and 2007, this paper estimates the inter-temporal variation in travel time and cost parameters (under the assumption that the variance of the error components of the indirect utility function is equal across the two datasets). It is found that the travel time parameter has remained constant over time but that the travel cost parameter has declined in real terms. The trend decline in the cost parameter can be entirely explained by higher average income level in the 2007 sample compared to the 1994 sample. The results support the recommendation to keep the travel time parameter constant over time in forecast models, but to deflate the travel cost parameter with the forecasted income increase among travellers and the relevant income elasticity of the cost parameter. Evidence from this study further suggests that the inter-temporal and the cross-sectional income elasticities of the cost parameter are equal. The average elasticity is found to be ?0.8 to ?0.9 in the present sample of drivers, and the elasticity is found to increase with the real income level, both in the cross-section and over time.     

Dynamic process model of mass effects on travel demand

Whereas transportation planners commonly predict the negative impacts of mass transportation, there is increasing empirical evidence of the existence of positive mass effects, whereby increased use of a mode by the ‘mass’ will generally increase its attractiveness for future travellers. In this paper we consider the dynamic impact of such an effect on the problem of travel demand forecasting, with particular regards to social network effects. Our proposed modelling approach is inspired by literature from social physics, evolutionary game theory and marketing. For simplicity of exposition, our model is specified for a scenario in which (a) there is a binary choice between two mobility lifestyles, referred to as car-oriented and transit-oriented, and (b) there are two population groups, where one is the “leading” or “innovative” population group and the other the “following” or “imitating” population group. This latter distinction follows the rather well-known Bass model from the marketing literature (1969). We develop the transition probabilities and transition dynamics. We illustrate with a numerical case study that despite lower intrinsic utility for the transit lifestyle, significant changes towards this lifestyle can be achieved by considering congestion, service improvements and mass effects. We further illustrate that mass effects can be positive or negative. In all cases we explore the sensitivity of our conclusions to the assumed parameter values.     

Do the selected Trans European transport investments pass the cost benefit test?

This paper assesses the economic justification for the selection of priority projects defined under the auspices of the Trans-European transport network. Three different transport models are used to analyse the costs and benefits associated with the current list of 30 priority projects. Most of these projects fail the cost-benefit test and few of the economically justifiable projects would need European subsidies to ensure their viability. Two remedies are proposed to minimise the inefficiencies surrounding project selection. The first remedy would oblige each member state or group of states to perform a cost-benefit analysis, followed by peer review and ensure that the results were published publicly prior to the ranking of federally funded priority projects. The second remedy would require federal funding to be made available only for projects with important spillovers to other countries in order to avoid pork barrel political behaviour.     

Time use,mobility and expenditure: an innovative survey design for understanding individuals’ trade-off processes

A large amount of information is required to model the complex trade-off processes between travel activities, non-travel activities and budget assignment at the individual level. This paper describes the development of a new survey design, which incorporates components of travel surveys, time use surveys and consumer expenditure surveys in an integrated format, which is expected to deliver a richer data set allowing deeper insights into individuals’ activity and consumption patterns. The survey procedure and the incentives paid, which were necessary to obtain acceptable response rates, are also described. Results from two pilot studies using a trip-based and an activity-based diary format are presented. The paper examines to which extent the diaries have been capable of collecting the required data with high quality and response rates. The innovative “Mobility–Activity–Expenditure-Diary” is introduced and results of the main survey using this design are presented. Travel behaviour and non-travel activities were reported at high quality. Expenditures would require longer observation periods (and preferably not only telephone but also personal support in the survey process) to reduce unsystematic variations and to better capture individuals’ long term equilibrium.

     

The bicycle-train travellers in the Netherlands: personal profiles and travel choices

Transportation - The Netherlands seems to exhibit the unique conditions that allow cycling on the country level instead of only the city level. Moreover, the national transit system seemingly...     

Second international conference on new survey methods in transport Hungerford Hill,Australia 12–16 September 1983

The Second International Conference on New Survey Methods in Transport was held at Hungerford Hill, Australia in September 1983. The aims of the conference were to provide a focus for discussion of survey methodology and to establish bench‐marks with respect to the state of the art in various facets of transport surveys. The conference evolved around workshops in twelve key areas: sample design, survey needs for modelling, questionnaire design and piloting, perceptual studies, diary surveys, longitudinal studies, interactive survey methods, freight surveys, traffic surveys, total design concepts, response errors and data correction, and coding and computing.

A number of plenary keynote papers were also presented describing the state of the art in cross‐sectional, longitudinal and interactive survey methods. Emerging from the conference discussions, six key issues were prominent; the gap between the state of the art, as espoused by researchers, and the state of practice, as employed by practioners; the differences in results obtained when employing different survey methods to collect essentially the same data; the emerging use of the telephone for the conduct of interview travel surveys; the interaction between survey methods and demand modelling and the disparate levels of sophistication in the two areas; the role of microcomputers in the design, conduct and analysis of transport surveys; and the need for practitioners to engage in controlled experimentation, so that methodological advances may continue to be made in the field of transport surveys.     

Planning for cycling in the dispersed city: establishing a hierarchy of effectiveness of municipal cycling policies

Transportation - Urban utility cycling is being promoted widely due to various health, social, economic and environmental benefits. This study seeks to identify and rank which municipal-level...     

A study on time constraints and task deviations at sea leading to accidents – a cultural-historical perspective

The high frequency of maritime accidents and incidents occurring at sea has been a major challenge for the maritime industry in the last decades. The majority of these accidents are attributed to seafarers’ poor performance. This, despite the fact that the international maritime domain continues to adopt and update conventions regulating maritime safety to mitigate these accidents from occurring. In this paper, utilising a qualitative research approach, we show through a socio-cultural contextual perspective that time constraints as a major influencing factor in causing task deviations at sea which leads to dangerous situations. We analyse how some of the present barriers in place to prevent accidents at sea are in effect prompt seafarers who are working under time pressure to deviate from their task. Moreover, the paper discusses the social constituents such as job insecurity and the seafarers’ viewpoint towards the ship operators’ commitment to safe ship operations are crucial in motivating seafarers’ deviating from the task at hand when faced with time pressure.