The pedestrian flow with evading and surpassing behavior in a walking passageway is simulated based on a modified social force model in order to explore the influence of this behavior on evacuation efficiency, bottleneck passing capacity, and the macroscopic phenomenon. A pair of conjugated self-driven forces is introduced to enable a pedestrian to avoid a direct collision and keep a normal velocity magnitude while confronting an obstacle. The pedestrian avoiding time is used to define the triggering conditions of evading and surpassing behavior, and has been estimated through practical experiments. Simulation results show that in a passageway without spatial obstacles, the evading and surpassing behavior will increase the evacuation time under the condition that the pedestrian number is larger than a critical value. Moreover, when a spatial obstacle exists, both the rise of pedestrian numbers and the decline of bottleneck width would increase the evacuation time. Meanwhile, it is observed that compared with a bar-shaped obstacle, a circle-shaped obstacle corresponds to a larger bottleneck passing capacity and less evacuation time when the size of the spatial obstacle is above a critical value. In addition, a phenomenon of a triangle ''evading region'' caused by the evading and surpassing behavior also can be observed before the spatial obstacle through simulation and experiments. Furthermore, it can be concluded that a circle-shaped obstacle corresponds to a stronger guiding function and a larger area of ''evading region'' compared with a bar-shaped one, and induces a relatively higher bottleneck passing capacity in a walking passageway.
In this paper, controlled experiments have been conducted to make deep analysis on the obstacle evading behavior of individual pedestrians affected by one obstacle. Results of Fourier Transform show that with the increase of obstacle width, the frequency and amplitude of body sway would barely be affected while the lateral deviation of walking direction would largely increase. On the one hand, the relation among the extracted gait features including body sway, stride length, frequency and speed has been illustrated. On the other hand, the walking direction can be featured by three critical evading points where apparent change of walking direction could be observed. Gaussian function has been used to fit the walking direction, thus allowing to estimate the three critical points and examine their variation with the increase of obstacle size. Furthermore, the direct-indirect evading and left-right turning preference as well as the possible psychological motivations behind have been analyzed. It is indicated that direct-evading pedestrians have a higher walking efficiency and right-turning pedestrians have a stronger tendency to behave 'direct'. Results of this paper are expected to provide practical evidence for the modeling of pedestrian dynamics affected by obstacles.
Pedestrian dynamics under adverse sight conditions is a difficult point in the field of pedestrian flow. In this paper, the simulation of pedestrian evacuation flow is carried out with blind herd mentality under adverse sight conditions. The pedestrian sight radius is introduced to describe adverse sight conditions, based on which blind following movement is adopted to describe the blind herd mentality of pedestrians in the door-invisible area. A special technology is introduced to compute the transition payoff in the dynamic parameter model to crystallize blind following movement, in which the concepts of choice vector, velocity vector, and direction similarity are introduced. Simulation results indicate that evacuation time under adverse sight conditions declines with increases in sight radius and gradually reaches a stable situation. It was found that evacuation time will rely on sight radius, initial density, and exit width. It was also observed that pedestrians blindly walk in herd-like patterns and crowd around the wall in the door-invisible area. Compared with the published model, the improved model is more effective in reducing evacuation time and dependence on sight radius. The extended model with internal layout and heterogeneous movement rules in a room is discussed as a possible future direction.
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