  The calibration and validation of pedestrian simulations require the
acquisition of empirical evidences of human behaviour. The current work
presents the results of an experiment focused on the potentially combined
effect of counter flow and grouping on pedestrian dynamics. In particular, we
focused on: (i) four different configurations of flow ratio (the rate between
the minor flow and the total flow in bidirectional scenarios); (ii) dyads, as
the most frequently observed and basic social groups of crowds. Results showed
that the increase of flow ratio negatively impacted the speed of pedestrians.
Dyads walked significantly slower than singletons, due to the difficulty in
movement coordination among group members (proxemics) in case of counter flow.
The collected results represent an useful contribution towards the validation
of pedestrian simulations.
