Empirical investigation on pedestrian crowd dynamics and grouping

The definition and implementation of pedestrian simulation models requires empirical evidences, acquired by means of experiments and on-field observations, for sake of model calibration and validation. This paper describes an observation carried out in a urban commercial-touristicwalkway (Vittorio Emanuele II Gallery, Milan, in collaboration with the Municipality of Milano). Although the analysis considered traditional metrics for describing pedestrian flow, such as the level of service, the main aim of this work was to quantify and characterize the presence, impact and behavior of groups in the observed population. In particular, we had confirmatory results on the frequency of groups in the observed situation, but we also achieved innovative results on trajectories and walking speeds: the walking path of individuals was 4% longer than the average path of groups, but the average walking speed of group members was 37% lower than the one of single pedestrians. Finally, a metric for characterizing group dispersion was defined and applied to the observed scenario: relatively large groups (size three and four) occupy more space in their movement when compared to couples. The achieved results represent useful empirical data for the calibration and validation of models for the simulation of pedestrians and crowd dynamics, but also for the development of automated techniques for data collection and analysis employing computer vision techniques.