Revisiting the theoretical basis of agent-based models for pedestrian dynamics

Robust agent-based models for pedestrian dynamics, which can predict the motion of pedestrians in various situations without specific adjustment of the model or its parameters, are highly desirable. But the modeller's task is challenging, in part because it mingles different types of processes (cognitive and mechanical ones) and different levels of description (global path planning and local navigation). We argue that the articulations between these processes or levels are not given sufficient attention in many current modelling frameworks and that this deficiency hampers the effectiveness of these models. Conversely, if a decision-making layer and a mechanical one are adequately distinguished, the former controlling the desired velocity that enters the latter, and if local navigation is not guided solely by intermediate way-points towards the target, but by broader spatial information (e.g., a floor field), then greater robustness can be achieved. This is illustrated with the ANDA model, recently proposed based on such considerations, which was found to reproduce a remarkably wide range of crowd scenarios with a single set of intrinsic parameters.Comment: arXiv admin note: substantial text overlap with arXiv:2309.1279

Diagrama fundamental del movimiento de peatones: Efecto de la competitividad

En este trabajo se ha estudiado numéricamente el proceso de evacuación de un conjunto de personas a través de una salida estrecha. Con este objetivo, se implementaron modelos de elementos discretos (DEM), de sistemas compuestos por partículas no esféricas autopropulsadas (peatones). Así, se desarrollaron nuevas metodologías de interacción entre peatones teniendo en cuenta la forma de la partícula y su correlación con la dirección deseada de movimiento. Para ello, se hizo uso de la estructura paralela de las unidades de procesamiento gráfico (GPU). Se ejecutó un estudio sistemático, ajustando varios parámetros del modelo, con el objetivo de reproducir condiciones experimentales específicas. Así, se varió la agitación de los individuos y la tendencia a mantener una dirección de movimiento deseada, manteniendo constante la magnitud de la velocidad deseada. Como punto de partida, hemos utilizado valores de flujo obtenidos experimentalmente, para validar si el modelo presenta una respuesta coherente. Además, se exploraron propiedades micromecánicas del sistema, como son: orientación de los peatones en posiciones cercanas a la puerta de salida y la proyección de estas sobre la dirección deseada. Finalmente, y motivados por los resultados experimentales muy recientes, hemos añadido un grado de complejidad al sistema, introduciendo un obstáculo. Las conclusiones que hemos obtenido han resultado del todo interesantes, en general obtenemos que introducir un obstáculo no resulta beneficioso para mejorar el flujo de personas. Así, nuestros resultados parecen contradecir opiniones preliminares de que la presencia de un obstáculo favorecería el proceso de evacuación. Sin embargo, reproducimos de manera fidedigna resultados experimentales, obtenidos muy recientemente, en el departamento de Física y Matemáticas de la Universidad de Navarra

Foundations of continuous agent-based modelling frameworks for pedestrian dynamics and their implications

This paper addresses the theoretical foundations of pedestrian models for crowd dynamics. While the topic gains momentum, widely different mathematical approaches are actually in use, even if we only consider continuous agent-based models. To clarify their underpinning, we first rephrase the common hierarchical decomposition into strategic, tactical, and operational levels and show the practical interest in preserving the continuity between the latter two levels by working with a floor field, rather than way-points. Turning to local navigation, we clarify how three archetypical approaches, namely, reactive models, anticipatory models based on the idea of times to collision (exemplified by the recently proposed ANDA model), and game theory, differ in their extrapolation of future trajectories, and insist on the oft-overlooked distinction between processes pertaining to decision-making and mechanical effects in dense settings. The differences are illustrated with a comparison of the numerical predictions of instances of these models in the simple scenario of head-on collision avoidance between agents, by varying the walking speed and the reaction times, notably

Spontaneous emergence of counterclockwise vortex motion in assemblies of pedestrians roaming within an enclosure

The emergence of coherent vortices has been observed in a wide variety of many-body systems such as animal flocks, bacteria, colloids, vibrated granular materials or human crowds. Here, we experimentally demonstrate that pedestrians roaming within an enclosure also form vortex-like patterns which, intriguingly, only rotate counterclockwise. By implementing simple numerical simulations, we evidence that the development of swirls in many-particle systems can be described as a phase transition in which both the density of agents and their dissipative interactions with the boundaries play a determinant role. Also, for the specific case of pedestrians, we show that the preference of right-handed people (the majority in our experiments) to turn leftwards when facing a wall is the symmetry breaking mechanism needed to trigger the global counterclockwise rotation observed

Modélisation de l’anticipation des collisions et des contacts dans la dynamique des foules piétonnes

International audienceSi les tragédies liées aux mouvements de foule viennent immédiatement à l’esprit à l’évocation de la dynamique piétonne, dans la majorité des cas, les piétons suivent des stratégies de navigation qui permettent de limiter le risque de collision et de se déplacer même dans des environnements très denses. Les modèles cherchant à reproduire la dynamique de foules peinent à restituer cette capacité de navigation et de faufilement. Nous proposons un cadre de modélisation “microscopique” de la dynamique piétonne qui, sortant du clivage entre approches robotiques et modèles de pseudo-forces, suit plus naturellement la séquence de processus à l’œuvre dans la nature. Pour cela, chaque agent choisit d’abord de manière autonome sa « vitesse désirée » comme optimum d’une fonction d’utilité (ou pseudo-énergie) sommant diverses contributions au sens physique clair, dont (i) un terme d’évitement des collisions [1], (ii) un terme de coût biomécanique, tous deux étalonnés empiriquement. Ensuite, une couche mécanique assure le traitement des éventuels contacts entre piétons.Ce modèle rend non seulement compte du diagramme fondamental, qui relie le flux de piétons à la densité pour un mouvement unidirectionnel, mais donne également lieu, dans un écoulement bidirectionnel, à un processus de formation de files quantitativement en accord avec des observations expérimentales. De plus, le sens physique des différents blocs du cadre de modélisation permet l’adaptation du modèle à des situations plus exotiques, comme l’inattention de plus en plus fréquente liée à la captation du regard par les smartphones et écrans. L’implémentation de cette idée dans le cas d’un flux bidirectionnel aboutit à des trajectoires devenant effectivement plus « chaotiques » (avec plus de virages brusques) en présence de piétons distraits, en accord semi-quantitatif avec les résultats d’expériences contrôlées [2]

Dinámica evolutiva en metapoblaciones complejas

Con este trabajo, pretendemos hacer uso del análisis de redes aplicadas a metapoblaciones para realizar una revisión de los recientes avances en la dinámica evolutiva de los juegos que se rigen por interacciones grupales. Nos centraremos principalmente en el juego de los bienes públicos (public good games) o de forma más general, en los juegos de N-jugadores (N-player games), que son representativos para este tipo de interacciones

Des fondations structurelles des modèles d'agents continus pour la dynamique piétonne et de leurs implications

This paper addresses the theoretical foundations of pedestrian models for crowd dynamics. While the topic gains momentum, widely different mathematical approaches are actually in use, even if we only consider continuous agent-based models. To clarify their underpinning, we first rephrase the common hierarchical decomposition into strategic, tactical, and operational levels and show the practical interest in preserving the continuity between the latter two levels by working with a floor field, rather than way-points. Turning to local navigation, we clarify how three archetypical approaches, namely, reactive models, anticipatory models based on the idea of times to collision (exemplified by the recently proposed ANDA model), and game theory, differ in their extrapolation of future trajectories, and insist on the oft-overlooked distinction between processes pertaining to decision-making and mechanical effects in dense settings. The differences are illustrated with a comparison of the numerical predictions of instances of these models in the simple scenario of head-on collision avoidance between agents, by varying the walking speed and the reaction times, notably

The role of anticipation among pedestrians in the emergence of stop and go waves

International audienc

Pedestrians in static crowds are not grains, but game players

The local navigation of pedestrians amid a crowd is generally believed to involve no anticipation beyond (at best) the avoidance of the most imminent collisions. We show that current models rooted in this belief fail to reproduce some key features experimentally evidenced when a dense static crowd is crossed by an intruder. We identify the missing ingredient as the pedestrians' ability to plan their motion well beyond the next interaction, whence they may accept to move towards denser regions for a short time. To account for this effect, we introduce a minimal model based on mean-field game theory, which proves remarkably successful in replicating the aforementioned observations as well as other daily-life situations involving collective behaviour in dense crowds, such as partial metro boarding. This demonstrates the ability of game approaches to capture the anticipatory effects at play in operational crowd dynamics