Study On The Moving Characteristics Of Individual Pedestrian Acrossing Dense Crowd

With the progress of society and the promotion of urbanization,large-scale crowd gathering activities,large-scale crowd activity places and high-density residential areas in cities are increasing.In special circumstances,dense crowds can easily evolve into crowded stampede accidents,which bring huge casualties and negative social impacts.How to ensure the safe activities of dense crowds and safe evacuation in emergency situations has always been the primary solved problem for relevant departments,scholars and event organizers.Pedestrian movement research has important practical significance for urban public crowd safety management.The research data and conclusions can provide corresponding scientific theories and basis for the safety planning and crowd safety management of crowd activity places.At present,scholar in the field of pedestrian motion gradually paid more attention to the research on the microscopic motion characteristics of pedestrians,but there are few researches on pedestrian crossing motion.Therefore,we designed and conducted individual crossing motion experiments for four scenarios,including low-density static crowds,high-density static crowds,low-density motional crowds,and high-density motional crowds.The global crowd density in the experimental area is set to 0～4.67 Ped/m~2,and in the actual experiment process,the local pedestrian density is as high as 8 Ped/m~2.In terms of individual microscopic motion characteristics,we use image processing method to extract the position data of experimental volunteer,and calculates individual crossing trajectory,crossing average speed,instantaneous speed,and crossing speed direction data.The study found that,to a certain extent,a smaller crowd density produces psychological stimulation for pedestrians crossing through,which is manifested in a more concentrated crossing trajectory and a higher crossing speed.When an individual pedestrian crossing through static crowd,most of the trajectories are repeated.Between 0 and 4.67 Ped/m~2of the global crowd density,the average individual crossing speed is linearly related to the density,and the individual crossing speed decreases monotonically with the increase of the crowd density.By comparing and analyzing the crossing experiments under the two experimental area sizes,it is shown that the individual crossing speed is affected by the crossing area length.Under the same crowd density,the average crossing speed of the individual crossing length is lower in the experimental area size.Between 0 and 4.67 Ped/m~2of the global crowd density,the average instantaneous speed of individual crossing decreases linearly with the increase of density,the speed along the crossing direction always dominates the total crossing direction speed,and the vertical crossing speed basically does not change with the density change.and the value is small.With the increase of crowd density,the direction angle of individual crossing speed shows a certain downward trend.The greater the instantaneous speed of individual crossing,the greater the fluctuation of individual crossing speed angle,and the angle of individual crossing through motional crowd is always lower than the angle of crossing through static crowd.Secondly,this paper adopts two quantitative characterization methods to calculate the local density of individuals,that is,the local density of the crowd.The first one is use the method based on Voronoi diagram to calculate parameters such as individual density,which is used to analyze the speed-density fundenmental diagram in the process of individual crossing motion.The crowd density shows a linear downward trend.When the individual density exceeds about 5 Ped/m~2,the linear decrease of pedestrian speed ends,and the curvature changes.As the crowd density continues to increase,the speed distribution remains basically unchanged.The second is a quantitative representation method of crowd aswarm degree based on individual spacing constructed in this paper.This method is used to analyze the spatial and temporal degree of individual aswarm degree in the movement of individuals.The results show that the individual aswarm degree can accurately reflect the crowded state of the individuals in the crowd.Several typical behaviors of individual pedestrians were observed in the experiment,such as detour,avoidance,change of speed and direction,and choice preference.This paper analyzes the mechanism and characteristics of individual pedestrian detour behavior from the perspective of individual aswarm degree.Individuals are sub-units that make up a crowd.In public activity places,pedestrian public transportation hubs,and sidewalks,individuals walk through behavior at all times.Collecting dynamic data of individual crossing movements and analyzing their behavioral characteristics can help researchers better understand individual pedestrians.The motion dynamics in the process of crossing is of great significance for ensuring the safety of large-scale crowds and the optimization and verification of crowd motion models.