  In this paper, the impact of holding umbrella on the uni- and bi-directional
flow has been investigated via experiment and modeling. In the experiments,
pedestrians are required to walk clockwise/anti-clockwise in a ring-shaped
corridor under normal situation and holding umbrella situation. No matter in
uni- or bi-directional flow, the flow rate under holding umbrella situation
decreases comparing with that in normal situation. In bidirectional flow,
pedestrians segregate into two opposite moving streams very quickly under
normal situation, and clockwise/anti-clockwise walking pedestrians are always
in the inner/outer lane due to right-walking preference. Under holding umbrella
situation, spontaneous lane formation has also occurred. However, when holding
umbrella, pedestrians may separate into more than two lanes. Moreover, the
merge of lanes have been observed, and clockwise/anti-clockwise pedestrians are
not always in the inner/outer lane. To model the flow dynamics, an improved
force-based model has been proposed. The contact force between umbrellas has
been taken into account. Simulation results are in agreement with the
experimental ones.
