Collective Dynamics (E-Journal)
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Video Analytics for Understanding Pedestrian Mobility Patterns in Public Spaces: The Case of Milan
Full text linkThe main objective of this research was to characterize public spaces through a mobility study on pedestrian patterns analyzed by means of video analytics (i.e., object detection, crowd counting, pedestrian tracking), for the case study of Piazza Duomo (Milan, Italy). The analysis focused on defining different pedestrian profiles through observable behavioural parameters (e.g., density conditions, speeds, trajectories, etc.). The results of the research could support the definition of an evidence-based approach for regeneration projects of urban public spaces
Effectiveness Verification of Evacuation Guidance Including Underground Passages Using Multi-objective Optimization
Full text linkIn this study, we approach the optimization problem of evacuation guidance assuming major terminal stations in Tokyo using crowd simulation and optimization algorithms. We propose a method to optimize multiple indicators with various guidance variables, including underground passages, and evaluate multiple scenarios obtained through optimization. The results of experiments using three algorithms: Random search, NSGA-II, and MOTPE, showed that MOTPE can be used to search for high-quality solutions quickly. Additionally, scenarios with guidance shortened the total evacuation time and reduced the congestion levels compared to scenario without guidance
Together Apart: the Influence of Increased Crowd Heterogeneity on Crowd Dynamics at Bottlenecks
Full text linkIndividual differences in mobility (e.g., due to wheelchair use) are often ignored in the prediction of crowd movement. Consequently, engineering tools cannot fully describe the impact of vulnerable populations on egress performance. To contribute to closing this gap, we performed laboratory experiments with 25 pedestrians with varying mobility profiles. The control condition comprised only participants without any additional equipment; in the luggage condition and the wheelchair condition, two participants at the center of the group either carried suitcases or used a wheelchair. We found that individuals using wheelchairs and to a lesser degree those carrying luggage needed longer to pass through the bottleneck, which also affected those walking behind them. This led to slower times to fully clear the bottleneck in the wheelchair and luggage condition compared to the control group. The results challenge the status quo in existing approaches to calculating egress performance and other key performance metrics in crowd dynamics
Heterogeneity of Agents in Cellular Evacuation Model Explains the Decreasing Bottleneck Flow
Full text linkHeterogeneous crowd consisting of pedestrians with essentially diverse abilities behaves in certain aspects differently than a homogeneous crowd consisting of "average" pedestrians. This study investigates the influence of heterogeneity in aspects connected to the ability to navigate through a crowd in front of a bottleneck. Simulations of cellular multi-agent model suggest that the heterogeneity in ability to push through the crowd (represented by aggressiveness) and willingness to bypass the crowd (represented by sensitivity to occupation) may be responsible for the bottleneck flow decreasing in time – a phenomenon observed in experiments
Classification of Pedestrian Crowds by Dimensionless Numbers
Full text linkPresently, classifications of pedestrian crowds primarily rely on density. This fails to encompass the diverse behaviours and risk profiles observed. We introduce two dimensionless numbers, the Intrusion number In, based on the desire to maintain one’s personal space, and the Avoidance number Av, based on the anticipation of collisions. These two numbers delineate different flow regimes, as we intuitively expect and as we empirically demonstrate using an extensive dataset. Similarly to Fluid Mechanics, where dimensionless numbers guide the choice between different approximations, the dynamics of crowds can be approached in each regime by perturbative expansions, which yield pedestrian models applicable in the corresponding regime (and only there)
Pilot Study of Mental Simulation of People Movement During Evacuations
Full text linkMental simulation of people movement forms a core component of pedestrian/evacuation analysis and planning, albeit one that is rarely addressed. It can be defined as the process by which a practitioner develops a narrative of how people within a built environment may move to inform a decision-making process regarding architectural or procedural design. There are a range of contexts in which a practitioner may use mental simulation. These can include assisting with identifying problems associated with architecture/procedural design and comparing with pedestrian/evacuation modelling results to suggest if these are in line with expectations.. Little research has been conducted exploring the process by which practitioners mentally simulate people movement, its efficacy, and what factors influence this process. This paper is intended to provide insights regarding this process. Results from an online survey are presented where expert practitioners where asked questions about a range of hypothetical evacuation scenarios with increasing complexity regarding what they expected the total evacuation time to be and how many people they expected to use each exit if they were simulated in a pedestrian/evacuation model. Participants were also asked how confident they were with their results. The survey data was then compared with results with evacuation model results of the same scenarios. Key findings from the study highlight that as the floor plan layout and behavioural complexity increase in a scenario, the greater the level of variation in responses between practitioners along with decreasing levels of accuracy and levels of confidence in their perceived ability for performing mental simulation of people movement. Floor plan and exit symmetry appear to influence a practitioner’s ability to mentally simulate people movement in terms of estimating evacuation times and exit usage when layouts/exit locations change
Viral Transmission in Pedestrian Crowds: Coupling an Open-source Code Assessing the Risks of Airborne Contagion with Diverse Pedestrian Dynamics Models
Full text linkWe study viral transmission in crowds via the short-ranged airborne pathway using a purely model-based approach. Our goal is two-pronged. Firstly, we illustrate with a concrete and pedagogical case study how to estimate the risks of new viral infections by coupling pedestrian simulations with the transmission algorithm that we recently released as open-source code. The algorithm hinges on pre-computed viral concentration maps derived from computational fluid dynamics (CFD) simulations. Secondly, we investigate to what extent the transmission risk predictions depend on the pedestrian dynamics model in use. For the simple bidirectional flow under consideration, the predictions are found to be surprisingly stable across initial conditions and models, despite the different microscopic arrangements of the simulated crowd, as long as the crowd evolves in a qualitatively similarly way. On the other hand, when major changes are observed in the crowd's behaviour, notably whenever a jam occurs at the centre of the channel, the estimated risks surge drastically
Evacuation of a Paediatric Hospital Ward in Italy: Lessons Learnt From an Announced Evacuation Drill
Full text linkThe process of evacuating a hospital ward is a complex task that involves several challenges related to emergency protocols, such as the need for assisted evacuation, the staff/patient ratio, and the functional limitations of patients. The purpose of this work is to present a possible sequence of events that can take place during an evacuation drill in a paediatric hospital ward. This is deemed to provide guidance in performing such type of drills and investigate assisted evacuation timelines. The drill was conducted inside a paediatric ward in Italy, at that time closed for maintenance, with the help of figurants emulating paediatric patients. The medical personnel were the ones normally working inside the facility. The activity was video recorded and summarised in a written report. This allowed the analysis of the drill and the reconstruction of typical set of events and timelines that take place in such type of evacuation drill scenarios
Revisiting the paper ”Simulating dynamical features of escape panic”: What have we learnt since then?
Full text linkThe paper "Simulating dynamical features of escape panic" by Helbing, Farkas, and Vicsek, published over two decades ago in Nature, has left an indelible mark on the field of crowd dynamics.With nearly 3,000 citations to date, according to the Web of Science records, this influential work has significantly shaped the field. This analysis investigates the overall influence of this paper through various indicators, documenting its reach across multiple research areas. The intellectual foundation of the paper is traced, examining the references cited and uncovering some misalignments between certain assertions and the citations meant to support them. The terminological impact is also explored, showing how the paper invigorated the use of terms like "panic" and "herding". Moreover, the alignment of some key assumptions of the paper with empirical evidence that has emerged since its publication is investigated, revealing discrepancies in key assertions about panic behaviour. It is also determined that the numerical observations of the paper have significantly influenced the field by introducing concepts such as the "faster-is-slower" phenomenon, on which empirical research has since produced mixed evidence rather than irrefutable support.While the paper remains a key pillar in crowd dynamics, we advocate for a new course for the field that could facilitate a paradigm shift in conceptualising crowd behavior, particularly one that reconsiders some terminologies and key behavioral concepts adopted in the paper, rather than treating them as proven
Propagation of Controlled Frontward Impulses Through Standing Crowds
Full text linkImpulse propagation in crowds is a phenomenon that is crucial for understanding collective dynamics, but has been scarcely addressed so far. Therefore, we have carried out experiments in which persons standing in a crowd are pushed forward in a controlled manner.Variations of experimental parameters include (i) the intensity of the push, (ii) the initial inter-person distance, (iii) the preparedness of participants and (iv) the crowd formation. Our analysis links the intensity of an impulse recorded by a pressure sensor with individual movements of participants based on head trajectories recorded by overhead cameras and 3D motion capturing data.
The propagation distance as well as the propagation speed of the external impact depends mainly on the intensity of the impulse, whereas no significant effect regarding the preparedness of participants could be found. Especially the propagation speed is influenced by the initial inter-person distance. From the comparison between two methods that detect the time of motion due to the impulse, a more sensitive result is obtained when the velocity of three landmarks of the human body is taken into account and not only the forward displacement of the center of mass. Furthermore, the more intertwined participants are in relation to each other, the more the impulse is distributed to the sides. As a result, more people are affected, however with smaller individual displacements