Building evacuation affected by mixed messages

21 November 2013

Research published this week in the Royal Society journal Interface has found that during evacuations, combinations of exit signs, memorised instructions and the movement of the crowd can affect how people leave buildings. 

Understanding how people exit buildings in an emergency is vital to avoid dangerous overcrowding at exits or bottle-necking of crowds in crisis scenarios. How different stimuli affect the decisions we make in such events can have major consequences. A team from the University of Essex have published work this week which investigates what influences the way people exit rooms in a simulated evacuation.

The team used a virtual environment to test how signs, memorised instructions and crowd movement influenced volunteers leaving a simulated environment. More than 500 participants took part in the computer-based study, each controlling a moving dot representing a person in the virtual world. Using a computer programme the volunteers were instructed to guide their avatar out of a simple room filled with other dot-like people through their choice of one of three exits.  

The researchers found that on their own, memorised instructions had little influence on the volunteers’ decisions of which exit to use. The volunteers were also left unfazed by the direction of the crowd, despite previous theory suggesting ‘herd-like’ behaviour whereby evacuees follow the crowd. The use of exit signs however, had a positive impact; influencing the volunteers to guide their avatars out of sign-posted exits.

However, in evacuation scenarios people are rarely faced with only one type of stimuli. They may have been given instructions on how to exit which reinforce or are contradicted by exit signs, and survivors of evacuations have spoken about the affect of surrounding people. The researchers led by Dr Nikolai Bode found ‘intriguing’ results when they analysed how the impact of these factors on their volunteers might be different when they were combined.  

The team say that “even memorised information that may not affect evacuees’ behaviour in isolation may become an important factor in human decision-making when combined with other sources of information”. When memorised instructions contradicted the direction of the displayed exit signs fewer people followed the sign-posted evacuation route. Similarly, when the crowd was moving in the opposite direction to the exit sign fewer volunteers tended to take the sign-posted exit. This finding suggests that tactical decision-making during evacuation is perhaps more nuanced than a reaction to a single stimulus.

Though the team admits there are questions about the extent to which their virtual simulation delivers results which reflect real life evacuation scenarios they do highlight the effect of mixed messages or contradicting stimuli in evacuation situations.