Evacuation Characteristics Of Preschool Children Passing Through Bottlenecks

In recent years,the number of preschool children has been increasing.It is of great significance to investigate the evacuation characteristics of preschool children to improve the evacuation efficiency and safety level.Bottleneck,as a typical structure in pedestrian facilities,has been widely investigated due to its constraint on pedestrian flow.However,current researches on pedestrian evacuation mainly focus on the evacuation characteristics of adults and ignore the difference of evacuation characteristics between preschool children and adults.The differences can provide support for the safety design and emergency plan of kindergartens and other facilities.Combined with current literatures,this paper conducts controlled experiments to study the movement characteristics of preschool children evacuating through bottlenecks and analyzes the influence of bottleneck width on children’s evacuation efficiency,and compares the difference of evacuation characteristics between preschool children and adults.Combined with the evacuation characteristics of preschool children,an agent-based model of preschool children passing through bottlenecks is proposed,and the empirical data are applied to validate the model.The influence of bottleneck width and number of pedestrians on evacuation characteristics are studied by applying the model.This paper carries out a labortary experiment of high-motivated preschool children and adults passing through bottlenecks as if in emergency.From the perspective of microscopic conflict,the evacuation characteristics of preschool children and adults are compared.By analyzing the spatial evolution of speed,the movement process of pedestrians can be divided into four stages:acceleration,deceleration,congestion,and re-acceleration.The movement direction angle of evacuation movement is defined and the direction angle changes from the stable small value in the initial stage to the larger value when the distance to the target is less than a certain threshold value.Pedestrians with high motivation gather around the bottleneck and form a typical arch-like density distribution.The peak density region formed by preschool children locates 0.30 m away from the bottleneck entrance.From macroscopic efficiency of preschool children and adults evacuating through the bottleneck,this paper investigate several characteristic time:evacuation activation time in the initial evacuation,acceleration time and waiting time in the process of evacuation,and evacuation time at the end of the evacuation.The acceleration time and speed of pedestrians accord with S-shaped function.The repetition of experiments show no obvious influence on the motion activation time of children.Flow normalization method is proposed to exclude the impact of body size and motivation of pedestrians on bottleneck flow and the proposed method better unifies the relation between flow and bottleneck width in different conditions.Based on the empirical study on the evacuation characteristics of preschool children,an agent-based model of preschool children passing through bottlenecks is proposed.By considering the velocities and positions of other pedestrians or obstacles in visual field,the proposed model determines the pedestrian movement direction.By considering the headway distance between pedestrians,the model can set the speed of simulated agent.The parameters of the model are defined by cross entropy method.The empirical data help validate the proposed model.The model can well reproduce the evacuation process of preschool children passing through typical bottlenecks.By applying the proposed model,this paper investigates the influence of bottleneck widths(0.60-2.00 m)and pedestrian number(20-100)on pedestrian flow.The bottleneck flow is found to have a piecewise linear relation with the bottleneck width.When the bottleneck width is higher than a certain threshold,the increase of bottleneck width shows no obvious influence on the flow.When the bottleneck width is lower than the certain threshold,the flow increases linearly with the increasing bottleneck width.In this paper,the model is also applied to simulate the evacuation of a kindergarten,and the optimized door width is proposed to improve the evacuation efficiency.The basic data of preschool children bottleneck evacuation obtained in this paper can provide data support for the research of preschool children evacuation.The investigation of movement direction and density distribution can provide help for the design of emergency plan for children’s facilities.The proposed agent-based model provides a common and effective method to assess evacuation efficiency of bottleneck structure.