Allelomimesis as escape strategy of pedestrians in two-exit confinements

Abstract

We study the efficacy of allelomimesis as an escape strategy of mobile agents (pedestrians) that aim to leave a two-exit room within the shortest possible time. Allelomimesis is the act of copying one’s kindred neighbors. To escape, an agent employs one of the following strategies: (1) It chooses its own route independently (non-copying, α = 0 ), (2) It imitates the actions of its neighbors at all times (blind copying, α = 1 ), or (3) It either copies or acts independently according to a certain probability that is set by the copying parameter α ( 0 < α < 1 ) . Not more than one agent could occupy a given room location. An agent’s knowledge of the two exit locations is set by its information content β ( 0 ≤ β ≤ 1 ) . When left alone, an agent with complete knowledge of the exit whereabouts ( β = 1 ) always takes the shortest possible path to an exit. We obtain plots of the (group) evacuation time T and exit throughput Q as functions of α and β for cases where the two exits are near (on same room side) and far (on opposite sides of room) from each other. For an isolated agent, T is inversely proportional to β . The chances of escape for an isolated agent with β ≤ 0.2 are higher with adjacent exits. However, for an agent with β > 0.4 the chance is better with opposite exits. In a highly occupied room (occupancy rate R = 80 % ) with adjacent exits, agents with β > 0.8 escape more quickly if they employ a mixed strategy of copying and non-copying ( 0.4 < α < 0.6 ). On the other hand, blind copying ( α ≈ 1 ) gives agents with β < 0.1 a better chance of escaping from the same room. For the same α and R values, opposite exits allow faster evacuation for agents with β < 0.1 due to the likelihood of streaming and the lower probability of exit clogging. Streaming indicates an efficient utilization of an exit and it happens when the arcs that are formed are smaller and arch interference is less likely. Allelomimesis provides a simple yet versatile mechanism for studying the egress behavior of confined crowds in a multi-exit room.