DisastersModern buildings have an alarming flaw when people need to escape quickly

By Achille Fonzone

Published 11 March 2016

The landscapes in which many of us live would have been unimaginable to previous generations. We now have skyscrapers so striking and tall they would make Icarus turn pale. Yet in emergency situations, our seemingly brilliant designs sometimes turn against us – and become death traps when disaster strikes. There is a major problem with the way we evaluate the safety of the structures in which we live and work. Until we address it, our chances of survival are a little like those of the characters from Greek legend – in the lap of the gods.

The landscapes in which many of us live would have been unimaginable to previous generations. We now have skyscrapers so striking and tall they would make Icarus turn pale. Yet in emergency situations, our seemingly brilliant designs sometimes turn against us – and become death traps when disaster strikes.

Safety engineering is about designing buildings that reduce the negative effects of accidents and attacks. The basic concept is straightforward: it takes a while after an incident before a structure collapses. If you can design it so that the time for everyone to flee is shorter than the time it takes to collapse, you save lives. This is the standard approach for big or complex structures in many countries, including the UK, US, Japan, Sweden and Italy.

But how long does it take to evacuate a building? It depends on the building and the escape routes, but crucially also on how people behave. To estimate the time it would take for everyone to flee – the “egress time” as we call it – safety engineers use computer simulations in which people evacuate after an incident and react to whatever happens around them.

The problem is that the simulations aren’t good enough – that’s what we have learned from detailed behavioural studies based on recent fires and terrorist attacks including 9/11 and the Mont Blanc tunnel fire of 1999 in which 41 people died. So either we teach evacuees to behave like our models – or, more realistically, improve our models.

This is not easy because the evacuee will make a host of different decisions: whether and when to start moving, in which direction, whether to respond to other evacuees, and which exit to use. Each choice also depends on how various factors interact with one another. Is the decision maker bold or risk-averse? Is there smoke in the room? How far away are the exits? And of most interest for our research purposes, what are the other evacuees doing?