The Impact of an Obstacle on Competitive Evacuation Through a Bottleneck

Within the last decade, a number of crowd accidents have attracted the interest of scientists to study the movement of crowd under high levels of competition. An interesting finding in crowd dynamics is that the presence of an obstacle at an appropriate distance in front of an exit can improve flow rate. A numerical simulation based on the discrete element method (DEM) and social force model was adopted in this paper in order to study the impact of obstacles on flow rate during competitive evacuation in two typical Settings with a single 0.8 m-wide exit. Setting I is a 15 m-wide room and Setting II is a 3 m wide corridor formed by the same room with lateral constrains. Numerical simulation in Setting I showed that a 1 m-obstacle at 1-m away from the exit can reduce evacuation time by approximately 49%. However, a contrasting increase of evacuation time by approximately 64% is observed in Setting II for the obstacle at the same location. To verify the findings, a number of experiments were conducted by compelling mice to escape under high competition in two similar settings. The general limitations of such experiments were accepted and described. These results were consistent with numerical simulations. This study demonstrates that whether an obstacle can improve the flow rate passing through an exit is dependent on the surrounding geometry.