A new collision avoidance model for pedestrian dynamics

The pedestrians can only avoid collisions passively under the action of forces during simulations using the social force model, which may lead to unnatural behaviors. This paper proposes an optimization-based model for the avoidance of collisions, where the social repulsive force is removed in favor of a search for the quickest path to destination in the pedestrian＇s vision field. In this way, the behaviors of pedestrians are governed by changing their desired walking direction and desired speed. By combining the critical factors of pedestrian movement, such as positions of the exit and obstacles and velocities of the neighbors, the choice of desired velocity has been rendered to a discrete optimization problem. Therefore,it is the self-driven force that leads pedestrians to a free path rather than the repulsive force, which means the pedestrians can actively avoid collisions. The new model is verified by comparing with the fundamental diagram and actual data. The simulation results of individual avoidance trajectories and crowd avoidance behaviors demonstrate the reasonability of the proposed model.

A new heuristics model of simulating pedestrian dynamics based on Voronoi diagram

A new heuristics model based on the Voronoi diagram is presented to simulate pedestrian dynamics with the noncrowded state, in which these mechanisms of preference demand evading and surpassing, microscopic anti-deadlock, and site-fine-tuning are considered. The preference demand describes the willingness determination of detouring or following other pedestrians. In the evading and surpassing mechanisms, in order to achieve a balance between avoiding conflicts and minimizing detour distances, a new pair of concepts: "allow-areas and denial-areas" are introduced to divide the feasible region for pedestrians detour behaviors, in which the direction and magnitude of detour velocity are determined.A microscopic anti-deadlock mechanism is inserted to avoid deadlock problem of the counter-directional pedestrian. A site-fine-tuning mechanism is introduced to describe the behavior of avoiding getting too close to the neighbors in pedestrian movement. The presented model is verified through multiple scenarios, including the uni-or bi-direction pedestrian flow in the corridor without obstacles, the uni-direction pedestrian flow in the corridor with obstacles, and the pedestrian evacuation from a room with single-exit. The simulation results show that the velocity–density relationship is consistent with empirical data. Some self-organizing phenomena, such as lanes formation and arching are observed in the simulation.When pedestrians detour an obstacle, the avoiding area before the obstacle and the unoccupied area after the obstacle can be observed. When pedestrians evacuate through a bottleneck without panic, the fan-shaped crowd can be found, which is consistent with the actual observation. It is also found that the behavior of following others in an orderly manner is more conducive to the improvement of the overall movement efficiency when the crowd moves in a limited space.

Cellular automata modeling of pedestrian＇s crossing dynamics

Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian’s crossing dynamics. A conception of “stop point” is introduced to deal with traffic obstacles and resolve conflicts among pedestrians or between pedestrians and the other vehicles on the crosswalk. The model can be easily extended, is very efficient for simulation of pedestrian’s crossing dy- namics, can be integrated into traffic simulation software, and has been proved feasible by simulation experiments.

Multi-grid simulation of pedestrian counter flow with topological interaction

We investigate the dynamics of pedestrian counter flow by using a multi-grid topological pedestrian counter flow model. In the model, each pedestrian occupies multi- rather than only one grid, and interacts with others in the form of topological interaction, which means that a moving pedestrian interacts with a fixed number of those nearest neighbours coming from the opposite direction to determine his/her own moving direction. Thus the discretization of space and time are much finer, the decision making process of the pedestrian is more reliable, which all together makes the moving behaviour and boundary conditions much more realistic. When compared with field observations, it can be found that the modified model is able to reproduce well fitted pedestrian collective behaviour such as dynamical variation of lane formation, clustering of pedestrians in the same direction, etc. The fundamental diagram produced by the model fits also well with field data in thc frce flow region. Further analyses indicate that with the increase of the size of pedestrian counter flow system, it becomes harder for the system to transit into a jamming state, while the increase of interaction range does not change the transition point from free flow to jamming flow in the multi-grid topological counter flow model. It is also found that the asymmetry of the injection rate of pedestrians on the boundaries has direct influence on the process of transition from free flow to jamming flow, i.e., a symmetric injection makes it easier for the system to transit into jamming flow.

Experimental study on age and gender differences in microscopic movement characteristics of students

Campus security has aroused many concerns from the whole society.Stampede is one of the most frequent and influential accidents in campus.Studies on pedestrian dynamics especially focusing on students are essential for campus security,which are helpful to improve facility design and emergency evacuation strategy.In this paper,primary and middle school students were recruited to participate in the single-file experiments.The microscopic movement characteristics,including walking speed,headway,gait characteristics(step length,step frequency and swaying amplitude)and their relations were investigated.Age and gender differences in the headway-speed diagram and space requirements were analyzed by statistical tests.The results indicated that the impacts of age and gender were significant.There were three stages for the influence of gender on the headway-speed diagram for both age groups.The impacts on students'space requirements were consistent for different age and gender groups.But the impacts of age and gender on free-flow speed were affected by each other.Due to the connection of walking speed and gait characteristics,the comparisons of gait characteristics between different ages and genders were performed to understand the corresponding differences in speed more deeply.The results showed that differences in step length and swaying amplitude between males and females were significant for both age groups.The effect of gender on step frequency was significant for primary students.But for middle school students,whether gender had significant impact on step frequency was not clear here because of the large P-value.Besides,the influence of age on gait characteristics changed with gender.

Using agent-based simulation to assess diseaseprevention measures during pandemics

Despite the growing interest in macroscopic epidemiological models to deal with threats posed by pandemics such as COVID-19,little has been done regarding the assessment of disease spread in day-to-day life,especially within buildings such as supermarkets where people must obtain necessities at the risk of exposure to disease.Here,we propose an integrated customer shopping simulator including both shopper movement and choice behavior,using a force-based and discrete choice model,respectively.By a simple extension to the force-based model,we implement the following preventive measures currently taken by supermarkets;social distancing and one-way systems,and different customer habits,assessing them based on the average individual disease exposure and the time taken to complete shopping(shopping efficiency).Results show that maintaining social distance is an effective way to reduce exposure,but at the cost of shopping efficiency.We find that the one-way system is the optimal strategy for reducing exposure while minimizing the impact on shopping efficiency.Customers should also visit supermarkets less frequently,but buy more when they do,if they wish to minimize their exposure.We hope that this work demonstrates the potential of pedestrian dynamics simulations in assessing preventative measures during pandemics,particularly if it is validated using empirical data.

Using Successive Multi-Goals Method in the Individual-Based Model to Simulate Crowd Behavior during Evacuation Processes

The fact of proportional population growth in many countries drags the attention of researchers in the field of crowd dynamics to the need for developing reliable models to predict the behavior of human crowds in emergency situations such as evacuation processes. Computer based models that simulate human crowd dynamics prove to offer the optimum way to predict the crowd realistic behavior especially in emergency situations. This paper presents a vital extension of my previous work in which an individual-based model to simulate the behavior of human crowd was developed using the artificial potential fields to describe the interaction forces between each crowd member and the environment on one side and amongst the crowd members on the other side to add realistic flavor to the predicted crowd behavior. In this paper, the successive multi-goals （SMG） method, which is a new method to represent the environment in which the crowd moves, is developed. Rather than using the traditional static potential field, the successive multi-goals method uses a dynamic potential field which is vital to solve the reactive problem that is considered as a drawback of the model when simulating the human crowd behavior during evacuation of buildings whose structures are complex such as bottlenecks and narrow corridors. Numerical results that match the real behavior of human individuals in emergency situations prove the efficiency of the new method to solve the problem on an individual basis as well as its applicability.

A derived grid-based model for simulation of pedestrian flow

We present a derived grid-based model for the simulation of pedestrian flow. Interactions among pedestrians are considered as the result of forces within a certain neighbourhood. Unlike the social force model,the forces here,as in Newtonian physics,are proportional to the inverse of the square of the distance. Despite the notion of neighbourhood and the underlying grid,this model differs from the existing cellular automaton(CA) models in that the pedestrians are treated as individuals. Bresenham's algorithm for line rastering is applied in the step calculation.

Efficient Dynamic Floor Field Methods for Microscopic Pedestrian Crowd Simulations

Floor field methods are one of the most popular medium-scale navigation concepts in microscopic pedestrian simulators.Recently introduced dynamic floor field methods have significantly increased the realism of such simulations,i.e.agreement of spatio-temporal patterns of pedestrian densities in simulations with real world observations.These methods update floor fields continuously taking other pedestrians into account.This implies that computational times are mainly determined by the calculation of floor fields.In this work,we propose a new computational approach for the construction of dynamic floor fields.The approach is based on the one hand on adaptive grid concepts and on the other hand on a directed calculation of floor fields,i.e.the calculation is restricted to the domain of interest.Combining both techniques the computational complexity can be reduced by a factor of 10 as demonstrated by several realistic scenarios.Thus on-line simulations,a requirement of many applications,are possible for moderate realistic scenarios.