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A two-dimensional (2D) Cellular Automata (CA) random model is developed to simulate occupant evacuation considering gathering behavior. The movement process from random distribution to gathering state can be simulated based on the map of the position repulsive force. Evacuations with random distribution and gathering distribution are compared. Visual field means object area coverage considered by the individual in the current cell, representing by the radius of visual field, VR. The simulation results with VR = 1 and 2 have little difference while the simulation with VR = 3 can reasonably represent gathering process. When the occupant density is less than 0.64 people/m2, the time of gathering process increases very fast with the increase of density; when the density is larger than 1.28 people/m2, the time of gathering decreases with the increase of density. When the initial density is less than 1.44 people/m2, the evacuation times with random distribution are always less than those with gathering distribution. When the initial density is larger than 1.44 people/m2, the evacuation times with gathering or random distribution are almost the same. Our model can simulate the gathering and evacuation process with more than two rally points. The number and distribution of rally points can deeply affect the evacuation time.

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