Empirical methods in pedestrian, crowd and evacuation dynamics: Part II. Field methods and controversial topics

Following the review of the experimental methods and top emerging topics, here, studies using the field data collection methods of pedestrian dynamics (April 2017-July 2019) are reviewed. This includes studies based on post-disaster analysis of real emergencies and past crowd incidents, field pedestrian observations in natural settings, and qualitative interviews with survivors of fire and other emergency incidents. The method of collecting field observations in natural settings is identified to be gaining increasing traction among other field methods (compared to the years preceding 2017) which in part reflects the recent growing attention to the calibration and validation of simulation models. Also, by assembling and analysing the entire body of empirical crowd literature from 1995 to 2019, this review identifies a list of controversial topics and puts a spotlight on recent experiments that have revisited and, in cases, challenged/modified certain long-held assumptions in crowd dynamics. Nine major controversial topics of crowd dynamics are identified for which mixed or contradictory empirical evidence exist. This includes questions related to the flow of pedestrians through bottlenecks (i.e. the faster-is-slower effect, partial obstruction effect, exit location effect, the nature of exit width-capacity relationship), as well as the decision-making aspects of pedestrian evacuations (i.e. the symmetry breaking phenomenon, and the effect of urgency level on various aspects of decision-making) and other topics such as the effect of social groups on evacuation efficiency or the effect of additional exits on blind evacuation efficiency. It is hoped that the discussions on these topics pave the way for further investigating and explaining these inconsistencies and settling the questions surrounding them.