Shuchao Cao

Pedestrian dynamics in single-file movement of crowd with different age compositions

An aging population is bringing new challenges to the management of escape routes and facility design in many countries. This paper investigates pedestrian movement properties of crowd with different age compositions. Three pedestrian groups are considered: young student group, old people group, and mixed group. It is found that traffic jams occur more frequently in mixed group due to the great differences of mobilities and self-adaptive abilities among pedestrians. The jams propagate backward with a velocity 0.4m/s for global density ρ_{g}≈1.75m^{-1} and 0.3m/s for ρ_{g}>2.3m^{-1}. The fundamental diagrams of the three groups are obviously different from each other and cannot be unified into one diagram by direct nondimensionalization. Unlike previous studies, three linear regimes in mixed group but only two regimes in young student group are observed in the headway-velocity relation, which is also verified in the fundamental diagram. Different ages and mobilities of pedestrians in a crowd cause the heterogeneity of system and influence the properties of pedestrian dynamics significantly. It indicates that the density is not the only factor leading to jams in pedestrian traffic. The composition of crowd has to be considered in understanding pedestrian dynamics and facility design.

Homogeneity and Activeness of Crowd on Aged Pedestrian Dynamics

An aging population is bringing new challenges to the management of escape routes and facility design in many countries. In this paper the movement properties of middle- and old-aged adults are studied with series of single-file movement experiments under laboratory conditions. The fundamental diagrams for two different groups of pedestrians and time-space diagrams are compared. For the groups with different composition and status, the fundamental diagrams are totally different but maintain the same trend. Active crowd leads to inhomogeneous pedestrian flow but higher flow rate, while inactive pedestrians prefer to keep pace with others or keep larger personal space, which leads to more jams and stop-and-go waves. Density and inhomogeneous of speed do not always play main roles on the appearance of stop-and-go.

An Extended Model for Simulation of Mexican Wave

Mexican wave is an interesting phenomenon in a stadium, and has attracted much attention. Some researchers have established models to reproduce it, and related mechanisms have been understood. However, the influence of some factors such as density and individuals visual field on this process has not been well investigated. Hence, this paper aims to simulate wave propagation by modifying a model introduced by Farkas et al. Detailed rules are given. After involving the effect of average density, it is observed that there will be a decrease in activation threshold if the average density decreases. This result is reasonable, and can be analyzed by calculations. Then, spectators visual field is considered in the model. The influence of initial locations of triggering group members on activation thresholds is discussed. Results demonstrate that it is easier to generate a wave at a relatively large average density if the location is in front rows of a stadium. It is hoped that this study will be helpful in a deep understand of the propagation mechanisms of Mexican waves and in crowd management.

Exit selection and pedestrian movement in a room with two exits under fire emergency

An extended multi-grid model is proposed to study fire evacuation in a two-exit room. The exit selection based on random utility theory, as well as the pedestrian movement in fire, is investigated. The effects of different occupant types, the utility threshold, heat release rate of fire, burning materials and pre-movement time on evacuation are discussed. The results show that active occupants are beneficial for evacuation because of their guidance to the herding pedestrians, whereas, the existence of conservative is not always good for evacuation; a proper frequency of changing target exit can relieve congestion and optimize evacuation process; evacuation time is not monotonically increasing with the increment of heat release rate due to acceleration when pedestrians feel the incentive of high temperature within limit; the effect of burning material on evacuation is related to its thermal physical properties; the pre-movement time aggravates the difficulty of evacuation due to the bad visibility and high CO concentration in fire situation. The study may be useful to predict exit selection and pedestrian movement process, and then give suggestions to guide pedestrian evacuation under fire emergency.

Fundamental Diagrams of Single-File Pedestrian Flow for Different Age Groups

In this paper properties of pedestrian movement are investigated with series of single-file experiments by considering the age composition of the crowd. Pedestrian trajectories with different age groups (young students group, old people group and mixed group) are extracted from the software PeTrack. It is found that the free velocity and maximum specific flow of young student group are the largest among three groups due to different mobility between young students and old people. More interestingly, the maximum specific flow of mixed group is smaller than that of old group, which indicates the jam occurs more easily in crowd composed of people with different movement abilities than that with homogeneous composition. At last, a nondimensional method considering pedestrian free velocity and body size is used to scale the fundamental diagrams for different age groups. The study is helpful to understand evolution of pedestrian dynamics with different ages.