Evacuation of the World Trade Center: what went right?

The evacuation of the World Trade Center on September 11, 2001 was not the first evacuation of the 110-storey high towers. Partial and full evacuations had taken place on other occasions. One particular event was the full evacuation of the two towers on Friday February 26, 1993 when a bomb exploded in the underground garage. The comparison of the 1993 and 2001 evacuations allows contrasting the occupants' understanding of the situation, their response and behaviour. Study results of the 1993 evacuation are compared to the analysis of first-person accounts found in the media following the 2001 disaster. It is concluded that the two full evacuations differ substantially. In September 2001, if the conditions had been similar to the ones experienced in 1993, many more occupants would have perished. The low number of fatalities below the floors of impact in 2001 suggests that several factors contributed to support the evacuation, which resulted in a successful evacuation for most occupants, located below the floors of impact