Method for guiding crowd evacuation at exit: The buffer zone

To control overcrowded pedestrians at the exit, buffer zones are very common in densely populated areas. However, little focus has been paid on the mechanisms of buffer zone. In this paper, a tentative experiment was designed to preliminarily reveal the role of buffer zone in crowd evacuation. Then a social force based simulation model was established by Massmotion according to the properties of the experiment. The simulated results show that buffer zones may have a potential positive effect on evacuation through comparing with the experimental results. After that, via changing the buffer zone length and the desired velocity of agents in further simulations, the data, such as evacuation time, density distribution, individual waiting time, instantaneous velocity and average velocity were investigated in detail. It is found that after the buffer zone set, the evacuation efficiency is significantly improved at high desired velocity, and the evacuation time is shortened with the increase in buffer zone length. Setting buffer zone in front of the exit can effectively reduce the crowd density at the exit, alleviate the surgent transmission of density waves in crowd, so as to reduce the risk of crowd squeezing and trampling. Besides, when the desired velocity is relatively high, the relationship between the buffer zone length and the average velocity is obtained specifically, indicating that the longer the buffer zone, the more likely pedestrians can escape as quickly as possible. Based on this work, some suggestions were put forward on how to control the dense evacuation via setting suitable buffer zones.