More gray hair—but for whom? Scenario-based simulations of elderly activity travel patterns in 2020

This paper reports the results of a scenario-based simulation study to explore mobility effects of an aging society in the Netherlands. Four accumulative behavioral scenario variants, embedded in an economic and demographic scenario are used to simulate possible future activity-travel patterns, using the Albatross system as the simulator. The variants account for likely differences in activity-travel behavior between elderly today and elderly in the future. Trends ongoing over the last decade in the Netherlands suggest that future elderly need to work longer, change their activity pattern with most growth occurring in the social/leisure activity category, will try to avoid morning peak hours by rescheduling their activities and may introduce more spatial diversity in terms of their residence location. Results show that these behavioral and spatial changes lead to a significant increase in travel demands as well as temporal, spatial and modal shifts in mobility patterns. We discuss possible policy implications of these predictions and evaluate the specific strength of activity-based models for studies of this kind.

Representing and estimating interactions between activities in a need-based model of activity generation

Although several activity-based models made the transition to practice in recent years, modeling dynamic activity generation and especially, the mechanisms underlying activity generation are not well incorporated in the current activity-based models. For instance, current models assume that activities are independent, but to the extent that different activities fulfill the same underlying needs and act as partial substitutes, their interactions/dependencies should be taken into account. For example, recreational, leisure, and social activities tend to be partly substitutable since they satisfy a common need of relaxation, and when undertaken together with others, social needs will be satisfied as well. This paper describes the parameter estimation of a need-based activity generation model, which includes the representation of possible interaction effects between activities. A survey was carried out to collect activity data for a typical week and a specific day among a sample of individuals. The diary data contain detailed information on activity history and future planning. Estimation of the model involves a range of shopping, social, leisure, and sports activities, as dependent variables, and socioeconomic, day preference, and interaction variables, as explanatory variables. The results show that several person, household, and dwelling attributes influence activity-episode timing decisions in a longitudinal time frame and, thus, the frequency and day choice of conducting the social, leisure, and sports activities. Furthermore, interactions were found in the sense that several activities influence the need for other activities and some activities affect the utility of conducting another activity on the same day.     

Foreland-based regionalization: Integrating intermediate hubs with port hinterlands

Development and changes in port hinterlands have received considerable attention as they represent substantial opportunities to improve the efficiency of global freight distributions. Port regionalization was a concept brought forward by Notteboom and Rodrigue (2005) to articulate the emerging port hinterland dynamics in light of containerization, supply chain management and the setting of inland terminals. This paper expands this concept by focusing on a particular dimension of the regionalization paradigm concerning the evolving role of intermediate hubs. It is argued that, in addition to hinterland-based regionalization, there is also a foreland-based regionalization where intermediate hubs capture a maritime hinterland. This intensity and viability of processes of foreland-based regionalization depend on multiple geographical, technical and market-related factors, and this paper identifies and analyzes these underlying parameters. By doing so, it assesses whether foreland-based regionalization is simply a transitional phase in port development or, alternatively, represents emerging functional characteristics of contemporary freight distributions.     

Experimental investigation of the strength and stability of submarine pressure hulls with and without artificial corrosion damage

A submarine may have to operate for a period of time with local corrosion damage in the pressure hull if a suitable repair method is unavailable or too expensive for implementation. This paper describes collapse tests on twenty ring-stiffened aluminium cylinders, which were conducted to study the effect of corrosion damage on hull strength and stability. Artificial hull thinning was found to reduce the collapse strength of experimental models through high local stresses in the corroded region, leading to early onset of yielding and inelastic buckling. Bending associated with the eccentricity due to one-sided thinning was found to further increase the local stresses in the hull. Overall collapse pressures were more severely affected by corrosion damage than interframe collapse pressures. The percentage reduction in overall collapse pressure, compared with intact experimental models, was found to be closely related to the percentage depth of thinning. The accuracy of conventional collapse pressure predictions for the experimental models was significantly better for intact than for corroded cylinders.     

IAME 2011 – contemporary studies on maritime transport in Latin America

Latin America and the Caribbean have evolved as a region of increased interest for the maritime and port industry as well as for academic research. Maritime transport activity in the region has experienced sustained growth rates over the last decades, resulting in ever-increasing demand for maritime services and port infrastructure. At the 2011 Annual Conference of the International Association of Maritime Economists (IAME), Latin America received significant attention. This editorial responds to growing research by giving a brief overview of the current situation and contemporary issues in maritime transport within the region. It also introduces the six selected papers for this Special Issue.     

Modelling Complex Activity‐Travel Scheduling Decisions: Procedure for the Simultaneous Estimation of Activity Generation and Duration Functions

Abstract

Activity generation is a key factor in individual's choices of trip frequency and trip purpose. This paper describes the results of an experiment conducted to estimate functions of several temporal factors on individuals' propensity to schedule a given activity on a given day. The theory on which the experimental design is based states that the probability of scheduling an activity is a complex and continuous function of how long ago the activity was lastly performed, the duration constraints for the activity and the amount of available time in the activity schedule of the day considered. Aurora, an existing model of activity scheduling, assumes S‐shaped utility functions for the history as well as the duration functions, whereas most time‐use studies assume monotonically decreasing marginal utilities. The stated‐choice experiment involves a range of flexible activities and a large sample of individuals to measure the utility effects of a set of carefully chosen levels for the factors and tests these specific assumptions. The results suggest that the amount of discretionary time on a day has no significant impact on the scheduling decisions provided that enough time is available for the activity. The effects of other factors are as expected and show diminishing marginal utilities. We find mixed evidence for an initial phase of increasing marginal returns as assumed in an S‐shaped function.     

Challenges for container river services on the Yangtze River: A case study for Chongqing

China plays an increasingly important role on the international economic scene and in global supply chains. Initially only coastal regions participated in global supply chains, but in recent years comparative cost advantages have led to an increased participation of inland destinations in China’s economic development. The growth of some inland regions has urged logistics players to revise and reconfigure their extensive logistics networks. This has been particularly the case in the Yangtze region. Upstream cities such as Chongqing are emerging as potential important production centres for the international markets.