La simulation à base d’agents en sciences sociales : une « béquille pour l’esprit humain »?

L’un des intérêts de la simulation informatique est de nous permettre d’explorer et d’essayer ainsi de comprendre des phénomènes contre intuitifs. Ce faisant, elle comporte aussi des dangers que le modélisateurs/simulateur doit savoir maîtriser. Le propos de ce court texte est de montrer que danger et enrichissement de la recherche vont de pair dans l’exercice de simulation. Ainsi, l’utilisation d’un appareillage formalisé est tout autant de nature à appauvrir qu’à enrichir notre tentative de compréhension des phénomènes sociaux. Le modèle de simulation joue alors un rôle heuristique très utile pour susciter de la complexité (enrichissement de notre vision) à partir de la simplicité (pauvreté du modèle). La souplesse du modèle et de son utilisation, permettant de refaire plusieurs fois l’expérience, de varier les angles d’approche, d’ajouter ou retrancher des paramètres donne au chercheur une grande capacité à maîtriser la complexité qu’il est alors capable d’instiller dans son investigation.Computer-assisted simulation allows us to explore and better understand phenomena which may at first appear counterintuitive. It also, however, entails certain risks which the modelization/simulation specialist must compose with. The object of this paper is to show that when it comes to simulation, dangers and virtues cannot be dissociated. Thus the use of a formalized model is as likely to empoverish as it is to enrich our understanding of social phenomena; the formalized model therefore plays a very important heuristic role in extracting complexity (enriching our vision) from simplicity (poorness of the model). The flexibility of the model as well as that of its use allowing to repeat the experience whilst varying the angles of approach and adding or modifying certain parameters of the experience, the researcher is given great opportunity to master the complexity which she/he may then instill in her/his investigation

À propos des flux transalpins de poids lourds : peut-on parler d’un « effet de barrière » suisse ?

De par la législation routière en vigueur sur son territoire, la Suisse constitue un îlot de réglementation au cœur d’une vaste zone de libre-échange. À ce titre, la confédération helvétique semble être à l’origine de déviations massives des flux transalpins de poids lourds vers certains passages alpins français et autrichiens. L’objectif de cet article est de proposer une évaluation qualitative (itinéraires et passages alpins concernés) et quantitative (volumes ainsi détournés) de ces hypothétiques reports de trafic, pour l’année 1994.The result of current road legislation in its territory is that Switzerland constitutes an island of regulation at the core of a vast zone of free exchange. The Swiss confederation seems to be the cause of massive detours of heavyweight transalpine traffic towards certain French and Austrian alpine crossings. The aim of this article is to propose both qualitative (involving paths and alpine crossings) and quantitative (number of trucks) evaluation of those hypothetical transfers for the year 1994.Nach der gültigen Strassenverkehrsordnung stellt die Schweiz auf ihrem Territorium eine Insel der Reglementierung inmitten eines grossen Bereichs mit freiem Austausch dar. Dadurch dürfte die schweizerische Eidgenossenschaft am Beginn gewichtiger Umleitungen im transalpinen Schwerlasterverkher hin zu französischen und österreichischen Alpenüberquerungen stehen. Ziel dieses Artikels ist der Vorschlag einer Evaluierung, die hypothetisch diese Verkehrsstruktur für das Jahr 1994 erfasst – sowohl qualitativ (alpine Reiserouten und Übergänge) wie quantitativ (Volumen der Umleitungen)

The role of space-time activity patterns in the exposure assessment of residents

International audienceIndustrial development can generate hazardous situations – in particular, when there is a need to deal with dangerous substances, such as those in chemical or petrochemical plants. Too often, these industries are located in the heart of urbanized areas with high-density populations, as urbanization intrudes on the hazardous sites (originally established outside of cities). Protecting civil populations from these risks – either through precautionary measures or special crisis management plans, if a catastrophe occurs – is a key issue. To better protect citizens, identifying the risks to which they are exposed and also how they perceive the risks in their area can help authorities and stakeholders better understand the risks (Glatron & Beck, 2008). Adequate knowledge of these risks can also dissuade populations from settling in certain zones and thus lower their vulnerability. Finally, authorities need to assess the exposure of populations to hazards – through modelling – to set up appropriate and efficient risk management plans based on land planning. The present chapter – founded on responses to a questionnaire-based investigation (see the Annex) carried out in the Milazzo–Valle del Mela area of Sicily, in 2008 – explores two main aspects of exposure assessment: space-time-pattern methodological challenges and results of individual space-time activity data extracted from the investigation in the Milazzo–Valle del Mela area

Future land use changes in a peri-urban context: local stakeholder views

Future land use/cover change (LUCC) analysis has been increasingly applied to spatial planning instruments in the last few years. Nevertheless, stakeholder participation in the land use modelling process and analysis is still low. This paper describes a methodology engaging stakeholders (from the land use planning, agriculture, and forest sectors) in the building and assessment of future LUCC scenarios. We selected as case study the Torres Vedras Municipality (Portugal), a peri-urban region near Lisbon. Our analysis encompasses a participatory workshop to analyse LUCC model outcomes, based on farmer LUCC intentions, for the following scenarios: A0 - current social and economic trend (Business as Usual); A1 - regional food security; A2 - climate change; and B0 - farming under urban pressure. This analysis allowed local stakeholders to develop and discuss their own views on the most plausible future LUCC for the following land use classes: artificial surfaces, non-irrigated arable land, permanently irrigated land, permanent crops and heterogeneous agricultural land, pastures, forest and semi-natural areas, and water bodies and wetlands. Subsequently, we spatialized these LUCC views into a hybrid model (Cellular Automata - Geographic Information Systems), identifying the most suitable land conversion areas. We refer to this model, implemented in NetLogo, as the stakeholder-LUCC model. The results presented in this paper model where, when, why, and what conversions may occur in the future in regard to stakeholders' points of view. These outcomes can better enable decision-makers to perform land use planning more efficiently and develop measures to prevent undesirable futures, particularly in extreme events such as scenarios of food security, climate change, and/or farming under pressure.info:eu-repo/semantics/publishedVersio

Le Calcul pour la simulation des systèmes complexes en géographie

National audienc

The Importance of Being Hybrid for Spatial Epidemic Models: A Multi-Scale Approach

International audienceThis work addresses the spread of a disease within an urban system, defined as a network of interconnected cities. The first step consists of comparing two different approaches: a macroscopic one, based on a system of coupled Ordinary Differential Equations (ODE) Susceptible-Infected-Recovered (SIR) systems exploiting populations on nodes and flows on edges (so-called metapopulational model), and a hybrid one, coupling ODE SIR systems on nodes and agents traveling on edges. Under homogeneous conditions (mean field approximation), this comparison leads to similar results on the outputs on which we focus (the maximum intensity of the epidemic, its duration and the time of the epidemic peak). However, when it comes to setting up epidemic control strategies, results rapidly diverge between the two approaches, and it appears that the full macroscopic model is not completely adapted to these questions. In this paper, we focus on some control strategies, which are quarantine, avoidance and risk culture, to explore the differences, advantages and disadvantages of the two models and discuss the importance of being hybrid when modeling and simulating epidemic spread at the level of a whole urban system

Simulating Urban Growth with Raster and Vector models: A case study for the city of Can Tho, Vietnam

Urban growth has been widely studied and many models (in particular Cellular Automata and Agent-Based Models) have been developed. Most of these models rely on two representations of the geographic space: raster and vector. Both representations have their own strengths and drawbacks. The raster models are simpler to implement and require less data, which explains their success and why most of urban growth models are based on this representation. However, they are not adapted to microscopic dynamics such as, for example, the construction of buildings. To reach such goal, a vector-based representation of space is mandatory. However, very few vector models exist, and none of them is easily adaptable to different case studies. In this paper, we propose to use a simple raster model and to adapt it to a vector representation of the geographic space and processes allowing studying urban growth at fine scale. Both models have been validated by a case study concerning the city of Can Tho, Vietnam

Influência da vizinhança nas alterações de uso/ocupação do solo urbano: o método LAND

As atividades humanas têm influenciado as alterações do uso/ ocupação do solo ao longo dos tempos. As alterações reagem às pressões demográficas, às tendências económicas e ao desenvolvimento dos transportes. O crescimento urbano com implicações nos padrões de alteração de uso/ ocupação do solo pode ser medido através de uma diversidade de métricas da paisagem. O nosso estudo é inspirado pela primeira lei da Geografia de Tobler, em que o autor afirma: tudo está relacionado com tudo, mas as coisas mais próximas estão mais relacionadas do que as coisas distantes. Neste artigo apresentamos o método LAND (LandusechAnge and Neighbouring Distance), construído no programa NetLogo, que permite identificar e medir a influência da distância vizinha no crescimento urbano a partir do limite das áreas urbanas existentes. Este método permite ser usado como suporte às políticas territoriais na monitorização da expansão urbana

Sistemas Multiagentes para a Modelação e Simulação de Alterações de Ocupação do Solo

Actualmente as áreas agrícolas no contexto das regiões metropolitanas apresentam fortes pressões urbanas. O uso do solo é transformado de acordo com diferentes decisões individuais de diferentes agentes do território. Neste estudo é feita uma abordagem das intenções dos agricultores sobre a transformação do território de acordo com diferentes cenários socioeconómicos utilizando um modelo baseado em sistema multiagentes (SMA). Este modelo visa a modelação das interacções entre estes actores e o território contribuindo para o apoio à decisão e propondo alternativas nas dinâmicas de ocupação do solo em contexto metropolitano (áreas urbanas e periurbanas). Esta investigação surge da relevância actual do uso do solo agrícola no contexto do ordenamento do território e das estratégias de desenvolvimento sustentável, nomeadamente da necessidade das políticas urbanas e regionais responderem eficazmente ao papel que cada vez mais as dinâmicas de ocupação do solo assumem em contexto urbano e periurbano. O modelo tem como caso de estudo o concelho de Torres Vedras com o seguinte conjunto de fases metodológicas: 1) Classificação do uso do solo em 8 classes, correspondendo ao tempo 0 do modelo (2010); 2) entrevistas realizadas a agricultores; 3) construção do modelo em multiagentes com definição dos Agentes, Território, Regras e Funções do modelo; 4) construção de cenários.info:eu-repo/semantics/publishedVersio

Estimating spatial accessibility to facilities on the regional scale: an extended commuting-based interaction potential model

<p>Abstract</p> <p>Background</p> <p>There is growing interest in the study of the relationships between individual health-related behaviours (e.g. food intake and physical activity) and measurements of spatial accessibility to the associated facilities (e.g. food outlets and sport facilities). The aim of this study is to propose measurements of spatial accessibility to facilities on the regional scale, using aggregated data. We first used a potential accessibility model that partly makes it possible to overcome the limitations of the most frequently used indices such as the count of opportunities within a given neighbourhood. We then propose an extended model in order to take into account both home and work-based accessibility for a commuting population.</p> <p>Results</p> <p>Potential accessibility estimation provides a very different picture of the accessibility levels experienced by the population than the more classical "number of opportunities per census tract" index. The extended model for commuters increases the overall accessibility levels but this increase differs according to the urbanisation level. Strongest increases are observed in some rural municipalities with initial low accessibility levels. Distance to major urban poles seems to play an essential role.</p> <p>Conclusions</p> <p>Accessibility is a multi-dimensional concept that should integrate some aspects of travel behaviour. Our work supports the evidence that the choice of appropriate accessibility indices including both residential and non-residential environmental features is necessary. Such models have potential implications for providing relevant information to policy-makers in the field of public health.</p