Forme urbaine et mobilité domicile-travail dans 13 aires urbaines françaises : une analyse multiéchelle

This article provides a multi-scale analysis of the links between commuting patterns and urban form by using both morphological and more classical indicators of urban form (like density). Thirteen French urban areas of more than 500,000 inhabitants (excluding Paris) are compared. The findings highlight the complexity of the links between urban form and commuting patterns because the same indicators of urban form do not have the same influence according to the spatial scale. Even if the influence of the morphological indicators is lower than that of more classical socioeconomic variables (income level, motorization rate), our study discusses the various and multi-scale consequences of urban development on daily travel behaviour.     

Review of empirical and semi-empirical Y factor solutions for cracked welded tubular joints

The practical use of fracture mechanics has been established for use on large turbine and electric generator rotor components used in the atomic power generation and the aircraft industry. Application areas in the offshore industry have also been identified. Fracture mechanics is currently used at the design stage of offshore facilities. It provides the basis for fatigue life prediction, steel selection and tolerance setting on allowable weld imperfections. Fracture mechanics is also used during the operational stage of a structure to make important decisions on inspection scheduling and repair strategies and as a tool for establishing limits on operational conditions. Linear elastic fracture mechanics relies on the use of the stress intensity factor concept. The stress intensity factor is a very important fracture mechanics parameter. Therefore, the accuracy of any fracture mechanics model for the prediction of fatigue crack growth in offshore structures for example will depend very much on the accuracy of the stress intensity factor solution used. Several empirical and semi-empirical solutions have been developed over the years with varying degrees of accuracy. This paper presents a review of some of these methods and attempts to assess their accuracy in predicting Y factors for welded tubular joints by comparing predicted results with experimental data obtained from fatigue tests conducted on large scale welded tubular joints. The experimental results were conducted under simulated service conditions, using a jack-up offshore standard load history (JOSH). A comparison between the experimental and predicted results shows that there may be other factors, which influence fatigue crack growth under variable amplitude conditions. Some of these factors have been identified and discussed in this paper.     

Shopping without travel or travel without shopping? an investigation of electronic home shopping

This study explores the growth of electronic home shopping in terms of likely transportation and communication interactions. Although opportunities exist to shop from home today, most consumers initiate travel trips to stores or markets. Widespread use of automobiles has facilitated the retailing configurations we know today but the development of new electronic networks could change this. This study establishes a baseline to explore shopping activities using two‐day travel activity data from a large U.S. metropolitan area. It is found that people who telework from home today spend more time engaged in shopping activities than other workers. Potentially, their saved work travel is converted into new trips. In the future, saved shopping travel might be converted into other types of travel, and modelling results show that for busy working women, there is a latent demand for maintenance‐related activities. The study results suggest that electronic home shopping will bring into play complex interactions between communications and transportation.     

Book review

Recreation: Marine Promise, Proceedings of the National Conference on Marine Recreation Susan H. Andersen, Ed., October 2–4, 1975, Newport Beach, California

Parable Beach: A Primer in Coastal Zone Economics by J. W. Devanney III, G. Ashe, and B. Parkhurst, The MIT Press, 1976, 99 pp.

Marine Recreational Fisheries, Proceedings of the First Annual Marine Recreational Fisheries Symposium Henry Clepper, ed., New Orleans, Louisiana, February 27, 1976.     

Livelihoods,daily mobility and poverty in sub-saharan Africa

Based on research funded by the UK Department for International Development, this paper investigates the utility of a livelihoods approach in identifying the mobility and accessibility needs of the poor. Mobility patterns and livelihoods of stratified samples of households in urban-to-rural corridors originating in the national capital cities of Zimbabwe and Uganda are compared, with emphasis on the poor's position relative to higher income groups. It is found that livelihood work was the most frequent purpose of short-distance travel for all income groups and localities, amounting to 38% of trip purposes in Uganda and 46% in Zimbabwe. On average, Zimbabweans were more mobile making more daily trips over longer distances reflective of greater reliance on motorized transport in the country. Nonetheless, walking dominates modal journeys in both countries. Ugandans display heavier dependence on bicycle and motorcycle transport primarily through taxi hire compared with Zimbabweans' private care and public kombi bus transport. Survey evidence suggests that Uganda's poor and middle-incomed urban and rural residents benefit from more widely available multimodal public transport.     

Agricultural vehicles and sustainable safe road traffic: solving conflicts on arterial highways

Addressing the issues of traffic safety in rural areas presents a constant challenge. The mix of light and heavy vehicles and the considerable differences in speed among these traffic participants result in high risks and delays for the faster vehicles. Agricultural vehicles (AVs) in particular have such an impact on traffic, especially when using arterial highways. This paper reviews the problems of safety and delays that AVs cause on arterial highways, and the appropriate mitigation. The concept of 'sustainable safety' in The Netherlands focuses on these problems, because of the proposed construction of parallel roads alongside all arterial highways. However, Dutch accident statistics cannot justify the high costs for the construction of parallel roads alongside 7000 km of arterial highways. Delays experienced by fast traffic are another reason for separating AVs from other road users with parallel roads. Alternative measures alongside the arterial highway, such as passing bays, restricting AVs to travelling at off-peak only and improving the conspicuity of the AVs, may be more cost-effective ways of reducing delays and/or improving traffic safety on arterial highways. Another solution may be to eliminate the need for AVs to use the arterial highway by altering their routes. For this purpose, land reallocation projects (as practised in Holland) can provide a useful tool.     

Bacterial production and microbial food web structure in a large arctic river and the coastal Arctic Ocean

Globally significant quantities of organic carbon are stored in northern permafrost soils, but little is known about how this carbon is processed by microbial communities once it enters rivers and is transported to the coastal Arctic Ocean. As part of the Arctic River-Delta Experiment (ARDEX), we measured environmental and microbiological variables along a 300 km transect in the Mackenzie River and coastal Beaufort Sea, in July–August 2004. Surface bacterial concentrations averaged 6.7 × 10⁵ cells mL^− 1 with no significant differences between sampling zones. Picocyanobacteria were abundant in the river, and mostly observed as cell colonies. Their concentrations in the surface waters decreased across the salinity gradient, dropping from 51,000 (river) to 30 (sea) cells mL^− 1. There were accompanying shifts in protist community structure, from diatoms, cryptophytes, heterotrophic protists and chrysophytes in the river, to dinoflagellates, prymnesiophytes, chrysophytes, prasinophytes, diatoms and heterotrophic protists in the Beaufort Sea.Size-fractionated bacterial production, as measured by ³H–leucine uptake, varied from 76 to 416 ng C L^− 1 h^− 1. The contribution of particle-attached bacteria (> 3 µm fraction) to total bacterial production decreased from > 90% at the Mackenzie River stations to < 20% at an offshore marine site, and the relative importance of this particle-based fraction was inversely correlated with salinity and positively correlated with particulate organic carbon concentrations. Glucose enrichment experiments indicated that bacterial metabolism was carbon limited in the Mackenzie River but not in the coastal ocean. Prior exposure of water samples to full sunlight increased the biolability of dissolved organic carbon (DOC) in the Mackenzie River but decreased it in the Beaufort Sea.Estimated depth-integrated bacterial respiration rates in the Mackenzie River were higher than depth-integrated primary production rates, while at the marine stations bacterial respiration rates were near or below the integrated primary production rates. Consistent with these results, P_CO2 measurements showed surface water supersaturation in the river (mean of 146% of air equilibrium values) and subsaturation or near-saturation in the coastal sea. These results show a well-developed microbial food web in the Mackenzie River system that will likely convert tundra carbon to atmospheric CO₂ at increasing rates as the arctic climate continues to warm.     

Attitudes to transport modes for shopping purposes in Singapore

A review of the retailing and transportation literature shows that there is an apparently large research gap in the understanding of shoppers’ attitudes towards transport modes for shopping purposes. In particular, not many studies have been done to examine shoppers’ detailed and disaggregated attitudinal image structures of the various transport modes for shopping purposes. Using Singapore as a study area, this paper has attempted to investigate shoppers’ image structure of transport modes and their comparative perception ratings for the various modes of transportation for shopping purposes. Using principal component analysis, the research has unveiled the perceptions of five transport modes for shopping purposes. While some of the factors are unique to certain transport modes, other factors, namely ‘suitability’, ‘practicality’, ‘ease of travel’ and ‘cost’, are common to all modes of transportation. By way of the weighted‐factor rating, the study found that the car recorded the highest overall perception rating while the bus rated the lowest. In addition, the shoppers have reasonably good perception of public transport modes in Singapore.     

Competing Visions for Marine Tenure and Co-Management: Genesis of a Marine Management Area System in Chile

Chile has been attempting to establish a Management Area (MA) system that melds the use of marine protected areas with marine tenure. The process has brought to the fore the competing interests of various user groups: artisanal fishermen, marine science professionals, government managers, tourist developers, and the Navy. We explore the core relationships among fishermen and the ecologists and biologists whose work is essential for establishing and maintaining a MA. The MA system's creation and implementation raise the key question of whether a marine tenure system can work under the conditions imposed by the Chilean government. There is a need to recognize and reconcile contradictions in a government management model that strives simultaneously to be a conservation zone and a financially profitable co-management zone. This article examines the MA management system's fault lines in the context of Chile's political economy, and the intimate interaction of management with fishermen's cultural survival strategies.     

Community Fishery Resources Management on Malalison Island,Philippines: R & D Framework,Interventions, and Policy Implications

In 1991, the Aquaculture Department of the Southeast Asian Fisheries Development Center launched a community-based fishery resources management project on Malalison Island, in central Philippines, to help conserve the country's marine resources and to help the fisherfolk rise above their poverty. The eight-year project integrated various disciplines in biology, economics, sociology, public administration, and engineering in its study of fishery resources and fishing communities and in evolving intervention strategies for resource conservation and management, and for community development. The project's most important accomplishment was the inculcation among the fisherfolk of the importance of resource conservation and management. The most important lesson learned was that an enlightened and empowered fisherfolk could be effective managers and responsible users of fishery resources.