Systematic experimental investigation of the obstacle effect during non-competitive and extremely competitive evacuations

Abstract

Although some experimental evidence showed that an obstacle placed in front of a door allows making people’s evacuations faster, the efficacy of such a solution has been debated for over 15 years. Researchers are split between those who found the obstacle beneficial and those who could not find a significant difference without it. One of the reasons for the several conclusions lies in the variety of the experiments performed so far, both in terms of competitiveness among participants, geometrical configuration and number of participants. In this work, two unique datasets relative to evacuations with/without obstacle and comprising low and high competitiveness are analyzed using state-of-the-art definitions for crowd dynamics. In particular, the so-called congestion level is employed to measure the smoothness of collective motion. Results for extreme conditions show that, on the overall, the obstacle does not reduce density and congestion level and it could rather slightly increase it. From this perspective, the obstacle was found simply shifting the dangerous spots from the area in front of the exit to the regions between the obstacle and the wall. On the other side, it was however confirmed, that the obstacle can stabilize longitudinal crowd waves, thus reducing the risk of trampling, which could be as important (in terms of safety) as improving the evacuation time. However, under urgent, competitive, but non-extreme conditions, the obstacle generally had a positive effect, helping channeling the flow of pedestrians through the exit while facilitating their interactions.

A novel social distance model reveals the sidewall effect at bottlenecks

“…The term “obstacle effect” describes the observation that under emergency evacuation conditions, the transportation at the bottleneck can be counterintuitively increased by a suitably placed obstacle near the exit. Many researchers have explored this topic using both simulation 15 , 16 and empirical 17 , 18 methods regarding, to name a few, the effect of obstacle size and position 19 , 20 , and the effect of corner exit rather than middle exit 21 , 22 . However, the obstacle and corner exit effects are applied to emergency escape conditions where the clogging results from the extremely small distance between individuals.…”

Experimental Study on Unidirectional Pedestrian Descending and Ascending Stair With a Fixed Obstacle

“…Many scholars have studied the influence of obstacle by performing experimental and simulation research. Up to now, studies on the topic of exploring the effect of obstacle on pedestrian motion features mainly focus on the effects of obstacle size [1], position [2,3], shape [4,5], spatial layout [6][7][8] and type [9] on evacuation efficiency and path selection features [10]. It has been found that obstacles influence pedestrian movement characteristics and evacuation efficiency [11].…”

On the dual effect of obstacles in preventing silo clogging

“…After this work, the increment of the flow rate by suitably placing an obstacle in front of the gate has been taken as a hallmark of pedestrian dynamics and, accordingly, it has been reproduced by most of the recently proposed models [2][3][4][5][6][7][8] . Nevertheless, a robust experimental demonstration of the obstacle effectiveness in pedestrian dynamics is still lacking given that the existing results are contradictory [9][10][11][12][13][14][15] . Paradoxically, this experimental evidence exists for other systems as i) the passage of animals such as sheep 16,17 or mice 18 through narrow doors, and ii) the discharge of granular matter from a silo [19][20][21][22] .…”