A heterogeneous lattice gas model for simulating pedestrian evacuation

Based on the cellular automata method (CA model) and the mobile lattice gas model (MLG model), we have developed a heterogeneous lattice gas model for simulating pedestrian evacuation processes in an emergency. A local population density concept is introduced first. The update rule in the new model depends on the local population density and the exit crowded degree factor. The drift D, which is one of the key parameters influencing the evacuation process, is allowed to change according to the local population density of the pedestrians. Interactions including attraction, repulsion, and friction between every two pedestrians and those between a pedestrian and the building wall are described by a nonlinear function of the corresponding distance, and the repulsion forces increase sharply as the distances get small. A critical force of injury is introduced into the model, and its effects on the evacuation process are investigated. The model proposed has heterogeneous features as compared to the MLG model or the basic CA model. Numerical examples show that the model proposed can capture the basic features of pedestrian evacuation, such as clogging and arching phenomena.     

Stair evacuation simulation based on cellular automata considering evacuees' walk preferences

As a physical model,the cellular automata(CA) model is widely used in many areas,such as stair evacuation.However,existing CA models do not consider evacuees' walk preferences nor psychological status,and the structure of the basic model is unapplicable for the stair structure.This paper is to improve the stair evacuation simulation by addressing these issues,and a new cellular automata model is established.Several evacuees' walk preference and how evacuee's psychology influences their behaviors are introduced into this model.Evacuees' speeds will be influenced by these features.To validate this simulation,two fire drills held in two high-rise buildings are video-recorded.It is found that the simulation results are similar to the fire drill results.The structure of this model is simple,and it is easy to further develop and utilize in different buildings with various kinds of occupants.     

An evacuation model using cellular automata

In order to simulate evacuation from a room with multiple exits, a two-dimensional basic cellular automata (CA) model is proposed based on human behavior. In this model, two factors are taken into account, viz. spatial distance and occupant density. To make the simulation more reasonable, human behavior including inertial effect, group effect and unadventurous effect are considered in an extended model. Numerical results show that the proposed CA model is realistic and robust. A parametric study reveals the potential application of CA model in the assessment of fire safety.     

Evacuation assistants: An extended model for determining effective locations and optimal numbers

The present research presents an extended evacuation field model for simulating crowd emergency evacuation processes under the control of evacuation assistants. Furthermore, a communication field for describing the escape information transmission process and its effect on evacuees is introduced. The effective locations and optimal numbers of evacuation assistants as generated through the model are proposed in an effort to verify as well as enhance existing models. Results show the following. (1) Locating evacuation assistants near exits reduces the time delay for pre-evacuation. (2) There is an optimal number of evacuation assistants for achieving evacuation efficiency; having excessive numbers of evacuation assistants does not improve the evacuation efficiency, and they may result in evacuation time delay and hinder the evacuation efficiency. (3) As the number of evacuees increases, the number of evacuation assistants needed decreases.     

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.     

Study on evacuation behaviors at a T-shaped intersection by a force-driving cellular automata model

A force-driving cellular automata model considering the social force on cell movement, such as the desirous willing of a pedestrian to exit, the repulsive interaction among pedestrians or between pedestrians and obstacles, was set up to investigate the evacuation behaviors of pedestrians at a T-shaped intersection. And an analogical formulation, taking reference of the magnetic force, was introduced to describe the above repulsive actions. Based on the model, the evacuation behaviors of pedestrians were simulated in terms of different pedestrian density, distribution and corridor width, and then evacuation time was obtained and analyzed. Furthermore, an experiment was conducted to verify the results of the presented model. The results demonstrate that when the density of pedestrians is greater than a certain threshold, pedestrians of a certain direction would be jammed by the repulsion from pedestrians of the counter flow from another direction, and the evacuation time of the former would be longer, even though they are closer to the exit, which would possibly result in a serious casualty in an emergency circumstance. And the phenomenon has been validated by the experiments well. In addition, a corresponding critical corridor width related to different DOPs, beyond which the evacuation time could be decreased rapidly due to a strong degradation of jamming behaviors near the T-shaped intersection, was also discovered and predicted by the proposed model.     

Incorporating topography in a cellular automata model to simulate residents evacuation in a mountain area in China

In China, both the mountainous areas and the number of people who live in mountain areas occupy a significant proportion. When production accidents or natural disasters happen, the residents in mountain areas should be evacuated and the evacuation is of obvious importance to public safety. But it is a pity that there are few studies on safety evacuation in rough terrain. The particularity of the complex terrain in mountain areas, however, makes it difficult to study pedestrian evacuation. In this paper, a three-dimensional surface cellular automata model is proposed to numerically simulate the real time dynamic evacuation of residents. The model takes into account topographic characteristics (the slope gradient) of the environment and the biomechanics characteristics (weight and leg extensor power) of the residents to calculate the walking speed. This paper only focuses on the influence of topography and the physiological parameters are defined as constants according to a statistical report. Velocity varies with the topography. In order to simulate the behavior of a crowd with varying movement velocities, and a numerical algorithm is used to determine the time step of iteration. By doing so, a numerical simulation can be conducted in a 3D surface CA model. Moreover, considering residents evacuation around a gas well in a mountain area as a case, a visualization system for a three-dimensional simulation of pedestrian evacuation is developed. In the simulation process, population behaviors of congestion, queuing and collision avoidance can be observed. The simulation results are explained reasonably. Therefore, the model presented in this paper can realize a 3D dynamic simulation of pedestrian evacuation vividly in complex terrain and predict the evacuation procedure and evacuation time required, which can supply some valuable information for emergency management.     

基于元胞传输模型的楼梯区域行人运动

针对楼梯区域行人运动进行观测实验,获得行人上下楼过程中的运动数据,通过对数据进行整理与分析,绘制不同过程中流量-密度变化关系图.通过对流密关系图进行定量分析,掌握楼梯区域行人运动特征,并改进原有元胞传输模型,提出楼梯行人运动模型,仿真模拟行人运动过程.模型中,引入势能修正系数,利用异向行人对元胞势能的影响来改变行人的路径选择;引入流量修正系数,描述不同的物理参数对元胞边界最大流量的影响;引入偏移系数,修正移动规则,增强优先方向对行人路径选择行为的影响.然后,通过比较仿真结果与实验数据,对模型及引入参数进行验证和校准.最后,利用校正模型,模拟研究楼梯区域对向行人运动过程,并对势能修正参数进行了灵敏度分析,进一步研究模型参数对行人运动的影响.研究表明,该模型可以模拟刻画楼梯区域行人运动过程,同时验证了楼梯区域行人集散效率跟行人到达率与行人路径选择有关.     

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 of pedestrian evacuation with asymmetrical exits layout

A simulation of pedestrian evacuation from a room with asymmetrical exit layout is presented based on the improved Dynamic Parameter Model in this paper. A special technique is introduced to compute two basic dynamic parameters: Direction-parameter and Empty-parameter considering the effects of pedestrian jam around exits and the width of exits on evacuation path selection in order to reduce evacuation imbalance caused by the asymmetry of exits layout. Two new coefficients: cognition coefficient and imbalance coefficient are introduced to respectively describe pedestrian cognitive ability and the layout imbalance of exits. The simulation results of the improved and original models are compared and analyzed. Simulation results show that evacuation time depends on the cognition coefficient and imbalance coefficient under normal evacuation condition with reasonable pedestrian. It is also found that there are phase transitions and critical points in the simulation curves of evacuation time against cognition coefficient and that the pedestrian flow shows distinctive characteristics at different phases. The values of critical cognition coefficient points depend on the initial pedestrian density and imbalance coefficient.     

Conflict game in evacuation process: A study combining Cellular Automata model

The game-theoretic approach is an essential tool in the research of conflicts of human behaviors. The aim of this study is to research crowd dynamic conflicts during evacuation processes. By combining a conflict game with a Cellular Automata model, the following factors such as rationality, herding effect and conflict cost are taken into the research on frequency of each strategy of evacuees, and evacuation time. Results from Monte Carlo simulations show that (i) in an emergency condition, rationality leads to “vying” behaviors and inhibited “polite” behavior; (ii) high herding causes a crowd of high rationality (especially in normal circumstances) to become more “vying” in behavior; (iii) the high-rationality crowd is shown to spend more evacuation time than a low-rationality crowd in emergency situations. This study provides a new perspective to understand conflicts in evacuation processes as well as the rationality of evacuees.     

Simulation of evacuation processes using a multi-grid model for pedestrian dynamics

Introducing the force concept of a social force model into the lattice gas (LG) model, a new LG-based discrete model entitled “multi-grid model” is composed. In the new model, finer lattice is used; thus each pedestrian occupies multiple grids instead of one, and the rules of interactions among pedestrians or pedestrians and constructions are built. The interaction forces including extrusion, repulsion and friction are considered as passive factors for evacuation. The strength of the drift, or the intensity of the pedestrians to move toward the exit rapidly, is considered an active factor. A simple situation is studied in which pedestrians try to evacuate from a large room with only one door. The influences of interaction forces and drift on evacuation time are analyzed. The mutual restriction relation of the two factors in the course of evacuating is found.     

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.     

Elastic inconsistency of the force constant models for body centred tetragonal indium

The origin of the elastic inconsistency of a lattice dynamical model is analysed by resolving the atomic displacements of body centred tetragonal indium, along three mutually perpendicular directions. It is shown that the angular forces which include the three-body interactions as well as the mixed neighbour interactions, are mainly responsible for the elastic consistency of the CGW model, whereas the remaining models which neglect these interactions become elastically inconsistent as we go from cubic to tetragonal symmetry. Hence the former is unique and not equivalent to any of the latter, but a certain degree of equivalence exists among the force constants of the DAF, MAS, GTF and CGW models. The role played by two-body, three-body interactions and same neighbour, mixed neighbour interactions, the distortions introduced into the phonon dispersion curves of indium by the elastic inconsistency as well as the consequences of imposing the rotational invariance conditions on the force constants of a lattice dynamical model for non-cubic solids are discussed.     

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.     

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.     

一个新的用于元胞自动机模拟微观组织的溶质分配模型及其计算验证

在已有的几种溶质再分配计算模型的基础上, 建立了一个新的更为合理的溶质再分配模型.该模型充分考虑了枝晶生长过程中可能出现的固/液界面元胞的各种状态及其邻居元胞的各种状态, 根据这两者的不同状态, 分别建立不同的计算公式展开计算. 利用所建立的模型消除了原有的扩散控制的元胞自动机(CA)生长模型存在的在晶界处元胞不凝固的缺陷. 接着, 为了进一步验证模型的可靠性, 在Kurz-Giovanola-Trivedi方法控制的CA生长模型中引入新的溶质再分配计算模型, 对Al-4.7 wt%Cu 合金铸锭进行了模拟计算, 并与实验结果进行了金相组织和成分分布两方面的对比, 表明新模型具有较好的精确性. 关键词： 元胞自动机方法 微观组织模拟 溶质再分配     

A refined cellular automaton model to rectify impractical vehicular movement behavior

When implementing cellular automata (CA) into a traffic simulation, one common defect yet to be rectified is the abrupt deceleration when vehicles encounter stationary obstacles or traffic jams. To be more in line with real world vehicular movement, this paper proposes a piecewise-linear movement to replace the conventional particle-hopping movement adopted in most previous CA models. Upon this adjustment and coupled with refined cell system, a new CA model is developed using the rationale of Forbes’ et al. car-following concept. The proposed CA model is validated on a two-lane freeway mainline context. It shows that this model can fix the unrealistic deceleration behaviors, and thus can reflect genuine driver behavior in the real world. The model is also capable of revealing Kerner’s three-phase traffic patterns and phase transitions among them. Furthermore, the proposed CA model is applied to simulate a highway work zone wherein traffic efficiency (maximum flow rates) and safety (speed deviations) impacted by various control schemes are tested.     

Measuring Dynamics in Evacuation Behaviour with Deep Learning

Bounded rationality is one crucial component in human behaviours. It plays a key role in the typical collective behaviour of evacuation, in which heterogeneous information can lead to deviations from optimal choices. In this study, we propose a framework of deep learning to extract a key dynamical parameter that drives crowd evacuation behaviour in a cellular automaton (CA) model. On simulation data sets of a replica dynamic CA model, trained deep convolution neural networks (CNNs) can accurately predict dynamics from multiple frames of images. The dynamical parameter could be regarded as a factor describing the optimality of path-choosing decisions in evacuation behaviour. In addition, it should be noted that the performance of this method is robust to incomplete images, in which the information loss caused by cutting images does not hinder the feasibility of the method. Moreover, this framework provides us with a platform to quantitatively measure the optimal strategy in evacuation, and this approach can be extended to other well-designed crowd behaviour experiments.