Flight Patterns

Some startled occupants inside Tower 1 at New York's World Trade Center on September 11 gasped while watching an incoming airplane disappear into the floors above them, while others heard the explosion that immediately followed. The building's swaying from the impact was so intense that some people thought the structure would "tip over." Observers closer to the impact site witnessed sections of the building on fire or chunks of the ceiling crash to the floor.

These first-person accounts, described in the 2005 report Analysis of Published Accounts of the World Trade Center Evacuation co-authored by Rita Fahy, NFPA's manager for Fire Databases and Systems, offered initial insight on conditions inside the towers and tenants' behaviors immediately following the terrorist attacks. Complementing the findings is new research analyzing what occurred once the survivors reached safety. Funded by the Centers for Disease Control and Prevention, To Leave An Area After Disaster: How Evacuees from the World Trade Center Buildings Left the WTC Area Following the Attacks analyzed survey responses from more than 1,400 survivors and identified concerns that researchers hope will strengthen emergency preparedness plans. The study was published in the May edition of Risk Analysis: An International Journal.

The evacuation below the planes' impact zones in Towers 1 and 2 was considered a "success" in both reports. During the attacks, the buildings housed approximately 17,400 people, and more than 14,000 were estimated to have escaped. Less than one percent of the total number of occupants-about 120 people-who presumably tried to evacuate floors below the impact zone died in the attacks. "When you compare the evacuation [during the 1993 World Trade Center bombing] with 9/11, there's a difference," Fahy says. "Building officials did a lot after the '93 bombing that facilitated the evacuation on 9/11."  

For instance, a new emergency communications system and photoluminescent path markings on stairs, railings, and stairwell doors guided occupants to safety, Fahy says. The new report concluded that fire safety training also affected occupants' behaviors. Forty percent of survey participants agreed that the safety information they received prepared them to evacuate the building, but only a quarter of survivors "felt they were provided with written fire safety information."

"What you had at this site is a lot of turnover and visitors," says Rae Zimmerman, the new study's co-author and professor at New York University's Robert F. Wagner Graduate School of Public Service. "It's not unusual for people not to be up to date on this [safety] material. What they ought to strive for is more frequent training and something more acceptable. You shouldn't rely on people reading instructions."

Survivors were also more inclined to search for their friends or make sure others were able to leave-confirming Fahy's observation that people under stress tend to seek others for comfort or watch how others behave to help guide their own reaction. Tenants also migrated down the stairwell in a calm and orderly fashion while helping others along the way-another evacuee commonality during emergency events, Fahy adds.   

Once they exited the buildings, most evacuees who didn't immediately leave the area indicated that they either stopped to see what was happening or searched for friends or coworkers. Nearly 30 percent of survey respondents stated they didn't know where to go. "You're talking about a whole bunch of people suddenly exiting an area with tremendous obstacles in their way," Zimmerman says. "People may have been familiar with the street [they exited onto], but not the area."

The new study also indicates there were no means of communication that let people know the city's subway system was shut down during the attacks. Moreover, survey respondents who lived outside of the city had a greater tendency to leave the immediate area than those living in the city. Immediate communication, says Zimmerman, is crucial for people to be able to identify a potentially hazardous situation and overcome another common belief during an actual emergency-denial of a threat. 

Zimmerman is working on a follow-up study that will compare the behaviors of evacuees inside and outside the towers during the attacks. The additional analysis could provide further insight into the adherence of specific emergency procedures, such as instructing all Tower 2 occupants to stay inside the building once the first plane hit the neighboring building. "That instruction was absolutely right at that moment," Fahy says. "There was debris falling, and a massive fire department response. You're not going to help by getting in the way. Nobody thought there was a second plane at that point. Nobody knew the towers were going to come down."