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International audience; Limiting commuting trips in major cities is important from the environmental, social and economic standpoints. In order to design policies that aim to change commuting practices it is, however, necessary to have acquired a good understanding of the trips in question and their determinants. However, these trips have been subjected to very little study in the cities of developing countries. This paper is concerned with the Rio de Janeiro Metropolitan Area (RJMA), and sets out to test the influence of “classical” socioeconomic and spatial variables on the distance and duration of the commuting trips of the region's inhabitants, especially those with the lowest incomes. The main original feature of this research is that it includes jobs in the informal sector. The results show that, all other things being equal, commuting distances and times are shorter for the informal sector, and people walk more from their homes to their place of work because jobs in the informal sector are more dispersed than jobs in the formal sectors. The notable exception is personal and household services for which employees (who are mainly women) live a long way from the city center where wealthy families (and their jobs) are concentrated.

International audience; In travel surveys, immobility is often approached as a technical issue that needs to be dealt with in order to measure mobility more accurately. By covering mobility patterns over a full week, the 2008 French Travel Survey allows immobility to be analysed other than as a marginal and random phenomenon. For working days alone, 28.8% of the adults in the survey had experienced one or more immobility episodes. By considering the intensity of immobility, and by introducing latent variables into Structural Equation Modelling, we have been able to propose a model with reasonable explanatory power. Our findings agree with previous studies and also show that within suburban or rural areas, access to shops or the type of local residential fabric are also factors that influence the number of immobile days. In addition, our findings show that the effects of the determinants differ between categories of individuals, notably between working adults and students on the one hand, and between retired and non-working people on the other.

International audience; Much has been spoken and written about the rationalization and optimization of services and amenities in urban territories. In this context, there is increasing use of numerical modeling techniques addressing the design, selection and/or calibration of policy instruments. The question of the relations between appraisal tools and policymaking has been widely studied. However, few studies have specifically focused on the role of modeling in policymaking processes. Drawing on two case studies, this paper suggests a change in the nature of multi-expertise: neither conflicting nor cross-sectoral, we observed in both cases an interwoven configuration with a network of experts making use of integrated models. We call this configuration distributed expertise, arguing that it is a novel configuration and that its emergence is closely linked to the development of integrated modeling techniques. Other authors have discussed the idea that the growing need for new appraisal tools is linked with the proliferation of wicked policy problems. From our case studies we would conclude that the emergence of integrated modeling is not a response to complex problems but to complex systems of actors who need to reach a consensus on actions.

International audience; The present article looks to pinpoint explanatory factors for the sharing of escorting of children in dual-earner families. It proposes a detailed analysis of inequalities and interactions in dual-earner families when it comes to escorting children by taking into account the characteristics of trips to and from school for children, the characteristics of the parents’ occupations, and the characteristics of the household. Compared with earlier research, the model considers more detailed data about the escorts’ jobs, such as specific working hours, which provide a better understanding of the constraints on parents and insight into the choices made when both parents are in a position to escort their children. The findings depart somewhat from those of earlier work on the question because more specific data are considered. They show a marked gender inequality in escorting because mothers in dual-earner families do more than two-thirds of the escorting. But the factors explaining the sharing of escorting act almost symmetrically for both parents, with the effect of work starting and finishing times being preponderant. These models confirm that the inequality kicks in ahead of this: mothers in dual-earner households are more often than fathers in jobs with short working hours and which are more compatible with escorting.

International audience; . Abstract The analysis of the evolution of transport networks can be performed by methods relating to the graph and network theory, for example by modelling the growth of the network or by analysing the evolution of global or local indices. However, this approach requires geographical databases representing the networks at different times. Maps are a natural source to create, by vectorisation, such geographical databases. We show in this article that, because of the particular nature of the cartographic representation that is a model of the territory rather than a mere image, it is necessary to explicitly take into account the modelling relation at the time of the map to be able to distinguish between the evolution of the territory and the art of the cartographer, rebuilding thus a kind of critical apparatus of the map.; L'analyse de l'évolution des réseaux de transport peut se faire par des méthodes issues de la théorie des graphes ou des réseaux, par exemple en modélisant la croissance du réseau ou encore en analysant l'évolution d'indicateurs globaux ou locaux au cours du temps. Cependant, cette approche nécessite de disposer de bases de données géographiques représentant les réseaux à différentes époques. Les cartes sont une source naturelle pour constituer, par vectorisation, de telles bases de données géographiques. Nous montrons dans cet article que, du fait de la nature particulière de la représentation cartographique qui est un modèle du territoire représenté et non une simple image, il est nécessaire de prendre en compte explicitement la relation de modélisation en vigueur à l'époque de la carte pour pouvoir faire la part de l'évolution du territoire et de l'art du cartographe, et reconstruire une sorte d'apparat critique de la carte.

This paper presents a new method for identifying urban fabrics based on population and build-up densities. It aims at creating a new zoning that embeds information about the composition of an urban area and its surroundings to help analyze the structuring role of transportation networks. The method allows for a more accurate characterization of areas sometimes ill-described in the zoning used in transportation studies. We developed a simple classification method transforming gridded data into radioconcentric grids thought to better fit European cities morphology. It provides a more adequate representation to retrieve urban fabrics. We apply our approach to datasets of the French cities of Besançon, Tours and Nancy, and compare the results to the zonings used in the last household travel surveys.; Cet article présente une méthode pour construire un zonage des tissus urbains sur la base des densités de population et de surfaces bâties. L'objectif est d'obtenir un zonage catégorisant l'étendue des agglomérations et de leur couronne périurbaine proche. Ce zonage se veut adapté pour l'analyse du rôle structurant des réseaux de transport et pour caractériser des zones périphériques parfois mal discriminées dans les zonages typiques des études de transport. La méthode répond à des critères de simplicité et d'indépendance vis-à-vis des maillages administratifs. Nous utilisons des densités initialement mesurées sur des grilles régulières, que nous transposons sur une grille radioconcentrique dont la structure morphologique semble plus adéquate pour caractériser et identifier les tissus urbains considérés. Testés sur les agglomérations de Besançon, Tours et Nancy, les zonages sont mis en situation par rapport aux découpages utilisés pour les dernières enquêtes ménages déplacements.

Digital Terrain Models constructed from contour lines often contain artifacts originating from their construction from irregularly spaced height measurements. We evaluate and illustrate these artifacts and their impact on terrain parameters. We provide algorithms to correct them as much as possible, and propose a methodology to predict areas where uncertainty still remains because of these artifacts. The analysis of these artifacts enables us to derive qualitative parameters such as "likely over-estimated", "likely underestimated", and "with no significant bias" on the DTM. Our method provides a qualitative description of local uncertainty, which is often more relevant for geographical applications than global quality parameters.