Fear propagation and the evacuation dynamics

Fear may spread over a crowd in a similar fashion as contagious diseases do in social groups. People in a life-threatening situation may express fear alerting others of imminent danger. This social mechanism initiates an evacuation process, while affecting the way people try to escape. We developed a model that describe and reproduce the fear propagation mechanism, where many individuals may suddenly switch to an anxious state. We focused on video analyses in order to obtain reliable parameters from a real fear-propagation events, and further test these parameters on computer simulations. We observed that two evacuation schemes may appear, according to the pedestrians susceptibility. Both schemes exhibit different evacuation patterns and are qualitatively visible in the available real life recordings of crowded events. We quantified these patterns through topological parameters. We further investigated how the fear spreading gradually stops if the source of danger ceases.