Insights toward characteristics of merging streams of pedestrian crowds based on experiments with panicked ants

Geometric design of egress and ingress configurations affects collective movement of pedestrians. Merging streams of pedestrian crowds is, in particular, one of the frequently observed features in public infrastructures and mass gatherings. However, few qualitative and quantitative studies have addressed this phenomenon in emergency situations because of the scarcity of data on human panic conditions. This paper studies the underlying geometric factors that affect dynamics and flow characteristics of merging streams in panic conditions through the use of nonhuman entities. Many experiments with panicked ants were performed in different angles and geometric characteristics. Flow rates, headway distributions, and escape speed of merging streams were studied. Results suggest that merging layouts can lead to the creation of stop-and-go phenomena and cause significant variation in the velocities of the joining paths over time. The authors also found that setups with tributary merging paths, in which a deviated stream joins a main branch, performed poorly compared with equivalent symmetrical setups. In addition, results show a dependency between traffic flow characteristics of the merged flow and the merging angle. Analyses also suggest nonexistence of a monotonic relation (or trend) between the merging angle and the merging throughput. This outcome specifically highlights the possibility of the presence of certain merging angles below and above which the overall flow performance is poorer (i.e., optimal angles). The findings provide a better understanding of the macroscopic characteristics of escaping flows in merging sections.