Pedestrians rotation measurement in bidirectional streams
  This study presents an experimental measurement of pedestrians' body rotation in bidirectional streams. A mock-up corridor monitored using a camera placed on azimuthal position is used to study pedestrians' behavior in unidirectional and bidirectional flows. Additionally, a commercial tablet is fixed on the chest of sample pedestrians to examine their body rotation (or yawing) which cannot be obtained using position tracking alone. Angular velocity is recorded and simultaneously stored in a central location using a wireless network, thus allowing the analysis of body movements with a high sampling rate and a limited delay. To investigate the influence of major/minor flow proportion (flow-ratio) on bidirectional streams two different situations were tested: the balanced configuration (with equal flows in both directions) and an unbalanced configuration (with different major and minor flow). Results clearly show that unidirectional flow is more stable compared to the bidirectional case, requiring less time to cross the experimental section and showing a very small amount of rotation during the whole experiment. Both bidirectional configurations showed high values of body rotation, in particular during lane formation and dissolution. Finally, rotation directly measured on pedestrians' body was compared with the one obtained indirectly by analyzing pedestrians' trajectories. The comparison shows that, at least from a qualitative point of view, both methods are in agreement, thus suggesting that even properties which can only be measured by motion sensing could be obtained indirectly through the analysis of trajectories. Concluding, it has been suggested that while lanes help smooth out bidirectional flows, larger instabilities are observed compared to the unidirectional case. Lane separation and/or appropriate guidance are therefore required. 
Claudio Feliciani and Katsuhiro Nishinari
physics.soc-ph