Final Reports of the Federal Building and Fire
Investigation of the World Trade Center Disaster
NIST NCSTAR 1-7: Occupant Behavior, Egress, and Emergency Communication
This report describes the occupant evacuation of World Trade Center (WTC)
1 and WTC 2 on September 11, 2001. Multiple sources of information were
collected and analyzed: over 1,000 new interviews with survivors (including
803 telephone interviews, 225 face-to-face interviews, and 5 focus groups);
over 700 published interviews; 9-1-1 emergency calls; transcripts of emergency
communications, historical building design drawings, memoranda, and calculations;
formal complaints filed with the Occupational Safety and Health Administration;
and other relevant materials. The egress system, including stairwells
and elevators, was described and compared to requirement of both contemporary
and current code requirements. This report documents the emergency procedures,
both as they were designed to be implemented, as well as how they were
actually implemented on September 11, 2001.
The population in WTC 1 and WTC 2 on September 11, 2001, at 8:46:30 a.m.
was enumerated and described, where the characteristics of the population
were relevant to the subsequent evacuation, including training, experience,
mobility status, among others. The progress of the evacuation of both towers
was described in a quasi-chronological manner from 8:46:30 a.m. when WTC 1
was attacked, until 10:28:22 a.m., when WTC 1 collapsed.
Causal models were built to explore the sources of evacuation initiation
delay (why people did not immediately start to leave the building) as well
as normalized stairwell evacuation time (how long the average occupant spent
in the stairwells per floor). Issues identified as contributing to either
speeding or aiding the evacuation process were explored. Egress simulations
provided context for estimating how long WTC 1 and WTC 2 would have taken to
evacuate with different populations, using different models, and subject to
different damage to the building.
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files for Project 1-7 may also be downloaded as a group within a
WINZIP (.zip) file. (5 MB)
