Contact forces and dynamics of pedestrians evacuating a room: the column effect
We report experimental measurements obtained during the evacuation of 180 soldiers through a narrow door. Several conditions are analyzed in the evacuation drills, such as the degree of competitiveness (from rush to shove) and the influence of an obstacle placed before the exit. From the data, we compute the flow rate through the door and the velocity and density fields, as well as a map of the local evacuation time. We also present novel results on the pressure that the individuals exert on the wall adjacent to the door. Our study challenges the idea that an obstacle could be beneficial for pedestrian evacuations because of a hypothetical alleviation of pressure at the door. At the same time, we discover a correlation among the largest pressure peaks and the development of clogging.