Since the tragic events of September 11, 2001, the US has gone to great lengths to secure commercial aircraft against terrorist attacks. However, a new study found rail and subway systems are increasingly becoming the target of terrorist plots.
In his study, Has Successful Terror Gone to Ground?, Professor Arnold Barnett of the Massachusetts Institute of Technology Sloan School of Management analyzed terrorist attacks over a 30-year period from 1982 to 2011. His paper was published in the online version of Risk Analysis, a publication of the Society for Risk Analysis.
Barnett found that, by far, the deadliest attacks against air and rail in the decade 2002−2011 were against subway and commuter rail systems. Prior to September 11, 2001, air travel was more likely to fall victim to a terrorist attack than virtually any other activity. However, Barnett asserted that, recently, “Many of the most publicized acts of terror have taken place on subways, commuter trains, and long-distance rail services.”
“This apparent shift raises the question of whether successful terror against transportation systems has ‘gone to the ground’ since the September 11 attacks against aviation,” Barnett said.
Worldwide, there have been 87 acts of successful terrorism which Barnett broadly defined as “all deliberate acts that cause multiple deaths to passengers” against air and rail transport systems between 1982 and 2011. Barnett analyzed these attacks in three successive decades: 1982-1991, 1992-2001, and 2002-2011.
Barnett discovered that, “Between 1982-1991 and 2002-2011, the number of air travelers killed in acts of terror fell by a factor of seven, whereas rail deaths increased over that period by a factor of seven. The increase was especially dramatic for subway/rail commuters.”
The total number of events showed very little variation from decade to decade; however, the percentage of fatal attacks targeting aviation dropped sharply during this period. Sixty-three percent of fatal attacks targeted aviation between 1982 and 1991, but that number dropped sharply to 28.6 percent from 1992 to 2001 and then declined to 9.4 percent in the following decade.
During this time, passengers killed in terrorist attacks targeting rail lines increased. While Barnett said the statistics do not imply this pattern will continue to be the case in the future, the statistics provide insight into the risk that terrorist acts pose to air and rail passengers.
Barnett contends that "if terrorists give weight to demonstrated success," then the vulnerabilities illustrated by recent rail bombings from Great Britain to Sri Lanka could be precursors to further attack. However, he also believes the pendulum could swing the other way, and that terrorists could again show greater interest in aviation as a target for attacks.
“It is obviously possible that both the level of air/rail terrorism and its split between aviation and railroads will change in the years ahead,” he said. “Of greater concern is the possibility that the future might be worse than the past.”
Some researchers have suggested terrorists take probability of success into account when choosing a target. Given the elaborate measures put in place in the wake of September 11, 2001, terrorists may not choose to renew focus on aviation. What is concerning, though, is many of the recent plots to attack aviation—such as the Richard Reid “Shoe Bomber” plot— have all failed.
In contrast, attacks against subways and commuter rails have achieved greater success. Barnett said, “By far the most deadly air/rail terror attacks over 2002-2011 were against subway/commuter rail systems, and they took 200 lives a piece.”
Barnett’s risk calculations did not include the 2,765 ground fatalities on September 11, 2001, since the report specifically only covers the risk terrorism poses to air/rail passengers. His analysis did not include deaths to third parties who were not passengers, events in which a passengerplane was mistakenly shot down by military sources unaware of its identity, or when a terrorist event includes several simultaneous attacks.
“Including these deaths in the calculations would give September 11, 2001 an overwhelming dominance in the analysis,” and “it could be unhelpful because the understandable preoccupation with that calamity can serve to obscure less extreme patterns related to acts of terror," he explained.
While acts of terror pose a miniscule risk to both air and rail travelers, Barnett said successful attacks nevertheless have far-reaching consequences. For example, there may have been no wars in Iraq and Afghanistan if the September 11, 2001 terrorist attacks had been thwarted. Moreover, many believe the 2004 commuter train bombings in Madrid may have changed the outcome of the Spanish national election days later.
Moving forward, Barnett contends intelligence, and not just security, will be crucial in preventing acts of terror on both air and rail transport systems.
“It was good intelligence work that averted a planned 2009 attack on the New York subway, not security measures at Times Square or Grand Central,” Barnett said.