Undesired body orientations in competitive pedestrian evacuations

We report time-resolved experimental measurements of human body orientation in extremely dense crowds during highly competitive evacuations. By comparing different scenarios, we find that as competitiveness increases and contact forces among pedestrians build up, orientational order deteriorates and undesired rotations emerge. This effect is markedly amplified when an obstacle is placed in front of the exit door; in some cases, this even causes individuals to rotate by 180°, forcing them to exit backward (i.e., facing away from the door). We propose that these undesired rotations are behind the previously observed lack of effectiveness of obstacles in improving flow during competitive evacuations: a finding that challenges long-standing assumptions. Furthermore, our results highlight the critical role of body orientation in the collective dynamics of dense human crowds, opening promising avenues for future research and crowd-management strategies.