Experiment and modeling of paired effect on evacuation from a three-dimensional space

A novel three-dimensional cellular automata evacuation model was proposed based on stairs factor for paired effect and variety velocities in pedestrian evacuation. In the model pedestrians' moving probability of target position at the next moment was defined based on distance profit and repulsive force profit, and evacuation strategy was elaborated in detail through analyzing variety velocities and repulsive phenomenon in moving process. At last, experiments with the simulation platform were conducted to study the relationships of evacuation time, average velocity and pedestrian velocity. The results showed that when the ratio of single pedestrian was higher in the system, the shortest route strategy was good for improving evacuation efficiency; in turn, if ratio of paired pedestrians was higher, it is good for improving evacuation efficiency to adopt strategy that avoided conflicts, and priority should be given to scattered evacuation.     

三维空间行人疏散的元胞自动机模型

为了有效刻画行人在三维空间中的疏散状况,结合阶梯因素提出了一种新的三维元胞自动机模型,该模型首先基于位置吸引力和碰撞可能性给出了行人移动概率的计算公式,并通过定义元胞演化过程阐述其疏散策略,同时,利用建立的仿真平台进行实验,深入分析了疏散时间、出口流率、出口宽度、初始行人密度以及系统平均速度之间的关系,以此获得更加符合实际情况的行人流特征,结果表明,疏散时间、出口流率与初始行人密度呈现正相关,而与出口宽度呈现负相关,并且系统平均速度和出口宽度对于最优疏散时间存在一个理想阈值。     

Experiment and multi-grid modeling of evacuation from a classroom

The evacuation process of students from a classroom is investigated by both experiment and modeling. We investigate the video record of the pedestrian movement in the classroom, and find some typical characteristics of the evacuation, including variable velocity, dislocable queuing, monopolizing exit and so on. Based on the experimental observation, we improve the multi-grid model by considering the pre-movement time of each pedestrian, adopting variable velocity and using a new update procedure. With the improved multi-grid model, we simulate the evacuation process and compare the simulation results with the experimental results, and find that they agree with each other closely. In order to analyze the uncertainty of evacuation, we investigate the influences of the pre-movement time and its distribution on the evacuation. It is found that the evacuation times exhibit a (truncated) normal distribution and vary within a region of about 30% of the mean value. An interesting phenomenon is that the evacuation time of the egress experiment is close to the minimum value calculated with the model, due to the coordination among pedestrians during the experiment. The study may be useful in developing applicable egress models and understanding the basic egress behaviors.     

Simulation study on cooperation behaviors and crowd dynamics in pedestrian evacuation

Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.     

Evacuation of pedestrians from a hall by game strategy update

In this paper, a cellular automaton model considering game strategy update is proposed to study the pedestrian evacuation in a hall. Pedestrians are classified into two categories, i.e., cooperators and defectors, and they walk to an exit according to their own strategy change. The conflicts that two or three pedestrians try to occupy the same site at the same time are investigated in the Game theory model. Based on it, the relationship between the pedestrian flow rate and the evacuation time as well as the variation of cooperative proportion against evacuation time is investigated from the different initial cooperative proportions under the influence of noise. The critical value of the noise is found when there is a small number of defectors in the initial time. Moreover, the influences of the initial cooperative proportion and strength of noise on evacuation are discussed. The results show that the lower the initial cooperative proportion as well as the bigger the strength of noise, the longer the time it takes for evacuation.     

基于元胞自动机的行人视线受影响的疏散流仿真研究

基于元胞自动机对视线受影响的行人疏散流进行仿真研究.模型根据行人视野半径将疏散空间划分为可见安全出口区域、可见墙壁区域和盲目区域;利用两个动态参数描述行人在不同移动区域内的疏散特征,从而决定行人的行为选择,包括行人定向移动、沿墙移动和正常疏散移动等行为.仿真研究了行人在墙壁上存在疏散指示标志的疏散空间内,视线受影响时采用随机定向寻墙沿墙移动疏散策略的情况下,行人视野半径对行人疏散时间的影响.研究表明,行人疏散时间不仅受行人视野半径的影响,而且还与安全出口的宽度和安全出口利用率有关.     

初始位置布局不平衡的疏散行人流仿真研究

行人初始位置布局不平衡的多安全出口疏散过程, 是行人疏散流仿真研究的热点. 利用行人流动态参数仿真模型, 在实际距离和假想距离"极大极小"路径选择机理的基础上, 改进假想距离的计算方法及其拥堵计算区域, 实现疏散过程的动态平衡; 提出行人位置布局的不平衡系数, 以描述疏散空间内行人初始位置布局的不平衡性. 从行人初始位置随机和固定布局的角度, 仿真研究正常疏散环境下行人布局的不平衡性对疏散时间的影响, 并将仿真结果与原始模型做对比分析. 研究表明, 模型能有效地实现行人流疏散过程的动态平衡, 行人疏散时间受行人位置或安全出口布局的影响较小, 而与安全出口总宽度、 行人的初始数量以及拥堵感知系数有关.     

Experimental study and numerical simulation of evacuation from a dormitory

The evacuation process of students from a dormitory is investigated by both experiment and modeling. We investigate the video record of pedestrian movement in a dormitory, and find some typical characteristics of evacuation, including continuous pedestrian flow, mass behavior and so on. Based on the experimental observation, we found that simulation results considering pre-movement time are closer to the experimental results. With the model considering pre-movement time, we simulate the evacuation process and compare the simulation results with the experimental results, and find that they agree with each other closely. The crowd massing phenomenon is conducted in this paper. It is found that different crowd massing phenomena will emerge due to different desired velocities. The crowd massing phenomenon could be more serious with the increase of the desired velocity. In this study, we also found the faster-is-slower effect. When the positive effect produced by increasing the desired velocity is not sufficient for making up for its negative effect, the phenomenon of the greater the desired velocity the longer the time required for evacuation will emerge. From the video record, it can be observed that the mass behavior is obvious during the evacuation process. And the mass phenomenon could also be found in simulation. The results obtained from our study are also suitable to all these buildings in which both living and resting areas occupy the majority space, such as dormitories, residential buildings, hotels (restaurants) and so on.     

An extended model for describing pedestrian evacuation under the threat of artificial attack

An extended floor field model was proposed to investigate evacuation behaviors of pedestrians under the threat of artificial attack. In this model, pedestrian movement governed by the static and dynamic floor field, and the motion and assault of artificial attacker were involved simultaneously. Further, injuries with lower velocity and deaths of pedestrians caused by the attacker during evacuation were considered. And a new parameter $k_t$ was introduced. It is the sensitivity coefficient of attack threat floor field and could reflect quantitatively the extent of effect of attack threat on the decision-making of the individual. Moreover, effects of several key parameters such as the sensitivity coefficient, assault intensity and pedestrian density on evacuation dynamics were studied. Results show that pedestrian evacuation would display interesting phenomena transiting from rolling behavior to along-the-wall motion with aggravating extent of the impact of attackers on pedestrians, which refers $k_t$ in the model varying from 0.5 to 0.8. As assault intensity increases, more casualties would be caused and the available evacuation time would decrease, which means people have to flee the room in a shorter time period for survival. When the pedestrian density increases, more clogging at the exit would be generated and pedestrians would be more difficult to evacuate due to the limited capacity of egress and the reduction in the average speed of pedestrian flow caused by the injured. And the injured with limited motion capacity could hardly complete the evacuation owing to that they need more evacuation time and would retard the speed of the pedestrian flow.     

Agitated behavior and elastic characteristics of pedestrians in an alternative floor field model for pedestrian dynamics

An alternative floor field (FF) model is proposed by incorporating the agitated behavior and elastic characteristics of pedestrians. The agitated behavior which is regarded as an important factor to pedestrian dynamics is depicted by introducing a parameter to revise the transition probability of pedestrians to move to the neighboring cells. To characterize elasticity of pedestrians, it is assumed that a cell can hold more than one pedestrians in crowd condition, while it can hold only one pedestrian in normal condition. In addition, a method to deal with conflicts is employed by considering the effects of agitated behavior and desired velocity. Numerical simulations are carried out to investigate pedestrian evacuation from a room. The results show, that as the value of agitated parameter increases, the evacuation time decreases to the minimum value and then increases gradually. Also, the faster-is-slower effect which is obtained by some other simulation models can be reproduced by the proposed model. Finally, the influence of exit width and the corresponding mechanism on evacuation process is investigated which is expected to be helpful to the exit design of public rooms.     

Modeling of pedestrian evacuation based on the particle swarm optimization algorithm

By applying the evolutionary algorithm of Particle Swarm Optimization (PSO), we have developed a new pedestrian evacuation model. In the new model, we first introduce the local pedestrian’s density concept which is defined as the number of pedestrians distributed in a certain area divided by the area. Both the maximum velocity and the size of a particle (pedestrian) are supposed to be functions of the local density. An attempt to account for the impact consequence between pedestrians is also made by introducing a threshold of injury into the model. The updating rule of the model possesses heterogeneous spatial and temporal characteristics. Numerical examples demonstrate that the model is capable of simulating the typical features of evacuation captured by CA (Cellular Automata) based models. As contrast to CA-based simulations, in which the velocity (via step size) of a pedestrian in each time step is a constant value and limited in several directions, the new model is more flexible in describing pedestrians’ velocities since they are not limited in discrete values and directions according to the new updating rule.     

Simulation of pedestrian evacuation based on an improved dynamic parameter model

An improved dynamic parameter model is presented based on cellular automata. The dynamic parameters, including direction parameter, empty parameter, and cognition parameter, are formulated to simplify tactically the process of making decisions for pedestrians. The improved model reflects the judgement of pedestrians on surrounding conditions and the action of choosing or decision. According to the two-dimensional cellular automaton Moore neighborhood we establish the pedestrian moving rule, and carry out corresponding simulations of pedestrian evacuation. The improved model considers the impact of pedestrian density near exits on the evacuation process. Simulated and experimental results demonstrate that the improvement makes sense due to the fact that except for the spatial distance to exits, people also choose an exit according to the pedestrian density around exits. The impact factors α, β, and γ are introduced to describe transition payoff, and their optimal values are determined through simulation. Moreover, the effects of pedestrian distribution, pedestrian density, and the width of exits on the evacuation time are discussed. The optimal exit layout, i.e., the optimal position and width, is offered. The comparison between the simulated results obtained with the improved model and that from a previous model and experiments indicates that the improved model can reproduce experimental results well. Thus, it has great significance for further study, and important instructional meaning for pedestrian evacuation so as to reduce the number of casualties.     

Discretization effect in a multi-grid egress model

In the traditional egress model based on cellular automata, building spaces are divided into discrete grids, the size of which is usually as large as that of a pedestrian. In order to explore the influences of the grid size on the evacuation results, we studied the evacuation process using a multi-grid egress model. In the multi-grid model, a finer grid is used and each pedestrian occupies n×n basic grids. It is found that if the pedestrian always moves one grid at each time step, the evacuation time increases with the decrease of the grid size, and reaches a stable, grid-independent value when the grid size is small enough. Another factor which influences the evacuation results is the length of the time step. It is found that with the increasing length of the time step, the evacuation time has a tendency to increase but endures complex changes. The differences between the single-grid model and multi-grid model may be due to two main reasons. First, in the multi-grid model, the pedestrians are out of alignment so that there are patches of unusable empty spaces as they are smaller in size than a pedestrian. Second, in the multi-grid model, pedestrians tend to reach the exit at the same time, leading to more serious conflicts among pedestrians.     

The excluded-volume effect in microscopic pedestrian simulations

We propose a pedestrian position update rule, which is added to a microscopic pedestrian model to avoid pedestrian overlap. In the rule, the step size of a pedestrian moving in a selected direction at each update is in inverse proportion to the repulsive actions imposed by other pedestrians moving in a direction with an exponential rate. The positions of the pedestrians are then updated in each small time interval. In this way, a barrier between the pedestrians can be generated, and after updating their positions the pedestrians do not overlap with each other. The modified model is compared to the original model through a simulation of the evacuation process of pedestrians in a closed area. The simulation results indicate that the modified model is superior to the original model in several aspects.     

Simulation of crowd dynamics in pedestrian evacuation concerning panic contagion: A cellular automaton approach

The study of the panic evacuation process is of great significance to emergency management. Panic not only causes negative emotions such as irritability and anxiety, but also affects the pedestrians decision-making process, thereby inducing the abnormal crowd behavior. Prompted by the epidemiological SIR model, an extended floor field cellular automaton model was proposed to investigate the pedestrian dynamics under the threat of hazard resulting from the panic contagion. In the model, the conception of panic transmission status (PTS) was put forward to describe pedestrians' behavior who could transmit panic emotions to others. The model also indicated the pedestrian movement was governed by the static and hazard threat floor field. Then rules that panic could influence decision-making process were set up based on the floor field theory. The simulation results show that the stronger the pedestrian panic, the more sensitive pedestrians are to hazards, and the less able to rationally find safe exits. However, when the crowd density is high, the panic contagion has a less impact on the evacuation process of pedestrians. It is also found that when the hazard position is closer to the exit, the panic will propagate for a longer time and have a greater impact on the evacuation. The results also suggest that as the extent of pedestrian's familiarity with the environment increases, pedestrians spend less time to escape from the room and are less sensitive to the hazard. In addition, it is essential to point out that, compared with the impact of panic contagion, the pedestrian's familiarity with environment has a more significant influence on the evacuation.     

Extraction and quantitative analysis of microscopic evacuation characteristics based on digital image processing

In this study, experiments of single-file pedestrian movement were conducted and the movement parameters of pedestrians were extracted with a digital image processing method based on a mean-shift algorithm. The microscopic characteristics of pedestrian dynamics, including velocity, density, and lateral oscillation, as well as their interrelations, were obtained and analyzed. Firstly, we studied the lateral oscillation phenomena of pedestrian movement. The result indicates that the trajectory of pedestrians presents a wavy form and the amplitude of the oscillation remains about 5.5 cm when the pedestrians move with free walking velocity, which is the velocity when there is no obvious interaction between sequential pedestrians; but when the movement velocity decreases to 0.27 m/s, the amplitude of oscillation increases to 13 cm. With increasing density, the velocity decreases and the amplitude of oscillation presents a linear increase trend. The increasing oscillation amplitude widens the occupation area of a pedestrian with low velocity, so as to make the moving efficiency even worse. Secondly, we studied the frequency of the oscillation; the result indicates that the frequency remains at 2 Hz when pedestrians move with a free walking velocity, but it presents a similar linear decrease trend when the velocity changes to a lower value. The decrease of oscillation frequency is also a negative feedback to the moving efficiency. Thirdly, it is found that with the increase of crowd density, the time interval between two sequential pedestrians increases, though the space gap between them decreases. The quantitative relation between time interval and crowd density is obtained. The study in this paper provides fundamental data and a basic method for understanding pedestrian dynamics, developing and validating evacuation models. The results are also expected to be useful for evacuation design.     

双出口房间人群疏散的实验研究和数学建模

本文设计了一个双出口房间内人群疏散的实验方案,通过不同条件下疏散过程的实况录像及视频检测,得到不同人数疏散时间的许多定量结果.提出了双出口房间吸引区间的概念,证明了较小出口吸引区间的边界总是一段圆弧,可以解释行人流出口处的圆形成拱现象.通过类比地铁候车厅内人群疏散过程,建立了双出口房间内疏散时间的二次函数模型,成功拟合不同条件下的实测数据.疏散人数较少时,疏散时间随着人数增加而线性增长;人数较多,在出口附近出现待行区域时,疏散时间则呈二次函数增长.与一些已知疏散时间数学模型相比,本文模型对出口宽度变化的反应更敏感.     

通过博弈的室内行人疏散动力学研究

在室内行人疏散过程中,行人博弈对疏散效率有着重要的影响.本文把抵制博弈策略更新的强度定义为抵制强度. 为了研究抵制强度对疏散效率的影响, 通过在行人博弈策略更新的概率中引入抵制强度,基于元胞自动机模型数值计算在不同的行人密度, 出口宽度下疏散总时间随抵制强度变化的关系.结果表明: 室内行人疏散过程中, 抵制强度小会使得争抢行为极其容易蔓延. 当行人密度小且出口宽大时, 输入以急速疏散为主的规范信息,鼓励行人模仿优胜者更新博弈策略, 当行人密度大且出口狭小时, 输入以避让为主的规范信息抑制行人争抢,都能提高疏散效率. 最后找出不同条件下与最短疏散总时间相对应的优化抵制强度, 为提高室内行人疏散效率提供一个新的视角.     

菱形网格的行人疏散元胞自动机模型

利用改进的层次域元胞自动机模型,研究了正菱形网格空间中的行人疏散问题.这类网格可以避免行人贴近房间墙壁或障碍物,转移概率考虑了各种逃生受阻因素.数值仿真显示,出口处的行人分布与实验快照展示的行人分布基本相同,疏散时间和出口宽度呈线性关系,行人流率接近实验结果.