That tragedy raised a number of questions, not least of which was what security measures can be put in place to prevent similar attacks by terrorists? While civilian aircraft are considered prime targets for terrorists and billions of dollars are spent each year to provide security for airline travelers, it would seem that too little is being done to protect the hundreds of millions of people riding subways in cities all around the globe.
However, answers to these questions have not been easy to find.
Almost exactly one year after the Daegu incident, at 8:30 a.m. local time on 6 February 2004, a powerful explosive device detonated in the second car of a train in the Moscow subway. The force of the explosion pushed out the metal sides of the car, tore a hole in the roof, and collapsed the car behind it. According to official figures provided to the RosBalt news agency on 17 February by the Federal Security Service (FSB), 40 people were killed.
Underground transportation systems are among the most difficult objects to protect from terrorist attacks. Given the huge volumes of travelers they service and the numerous stations they have -- in New York City, there are 468 stations, while London's underground has 273 stations -- it is nearly impossible to control the millions of passengers entering during rush hour carrying backpacks, shopping bags, attache cases, and the like -- or, perhaps, wearing a vest bomb concealed under a baggy jacket.
Subway systems, which have multiple turnstile entrances and where trains enter the station just minutes apart, create many more security challenges than airports, where large groups of passengers can be funneled to undergo screening and have their bags searched. Moreover, airplanes can be delayed if authorities deem it necessary, while subway lines must keep moving.
Checking public-transport passengers for explosives or flammable liquids in plastic or glass containers is an imperfect and often impractical solution. It would lead to long delays and still not be able to guarantee safety.
The U.S. General Accounting Office (GAO) has reported that, while there are a number of advanced explosives detection devices commercially available that can increase the probability of detecting concealed explosives, "all of them have performance limitations. "For example, some devices can detect only certain explosives, while others have slow luggage processing rates; others rely almost entirely on the skills of the operators rather than on automatic alarms," the GAO report reads. A summary of the GAO findings can be found at http://www.gao.gov/docsearch/abstract.php?rptno=RCED-97-119R
The use of security cameras to monitor the behavior of passengers inside subways has proven nearly useless. All they can monitor is a crowded passenger car or platform and might possibly show a person igniting a bottle filled with gasoline and show a split second of the flames that follow. The cameras have little defensive value beyond the slight chance they might capture a known suspect on film, providing the person monitoring the image knows whom to look for. Cameras also have a slight deterrent effect by signaling to a potential bomber that someone is watching.
One known example of police being able to disrupt a subway attack took place in New York City in 1997 when the FBI foiled a plan by two Palestinian would-be suicide bombers to detonate five pipe bombs at one of the city's major subway stations. The authorities apparently were able to thwart the plot through inside information.
"The Washington Post" reported on 9 April 2003 that: "Captured Al-Qaeda operations chief Khalid Sheikh Muhammad has told interrogators that his organization had plans to attack the Metrorail system in Washington, possibly by igniting a fire, according to law enforcement officials.... Two law enforcement sources said the attack on the Metro would have involved a fire or firebombing. One said the Capitol Hill area was a likely target."
The accuracy and reliability of this testimony can be debated, but there can be little doubt that Al-Qaeda has been looking into possible attacks on subways in cities like Washington, D.C., or New York City.
The coordinated attacks on the London subway system during the morning rush hour on 7 July, during which some 49 people were killed and hundreds injured, have once again raised questions about public-transport security.
The most common question being asked today concerns the use of coordinated attacks. How easy is it for a terrorist group to coordinate three or four attacks and thereby multiply the chaos and tax a city's emergency services? The answer is that there is nothing very complex in planning such attacks. For four or five members of a conspiratorial group to carry out simultaneous actions is not a recent development, nor is it anything that Al-Qaeda perfected.
During the Algerian war for independence, the Algerian nationalist organization FLN used this tactic often and launched coordinated bomb attacks against cafes, airline ticket offices, and other establishments in Algiers popular with the city's French population. Little more is needed than elementary communication and the ability to tell time.
Even primitive explosive devices can be rigged with timers to explode simultaneously.
Michael Oren of the Shalem Center think tank in Jerusalem was quoted by AP on 10 July as saying that coordinated attacks have become more sophisticated in Israel as well. "In Israel, we've had coordinated bombings, but they've never been that close," Oren said. "If they've got down to a minute that would be an all-time record. The use of timers is not rocket science, but it still shows a level of sophistication which is beyond just sending somebody with an [explosive] belt."
A time lapse between attacks of a few minutes is not uncommon and does not really matter since the evacuation of other Metro stations or trains after the first blast cannot begin so quickly.
In the London case, the explosive devices were reported by the press to have been crudely made bombs. On 8 July, AP quoted Andy Oppenheimer, a weapons expert and consultant for Jane's Information Group, as saying that the bombs were made from "relatively easy-to-obtain plastic explosives, not the higher-grade military plastics such as Semtex." Police said after the bombing that the bombs weighed less than 4.5 kilograms each.
Another factor acting in favor of the subway bomber is cost. Crude bombs such as the ones used in London, Moscow, or by the lone subway arsonist in South Korea are inexpensive to construct.
One expert quoted by the BBC gave an estimate of $10,000-$15,000 for the 7 July attacks in London. She said that since the bombs cost so little, it was probably possible for the organizers to raise the funds locally and avoid bank transfers that could attract the attention of the authorities.
Gasoline might just be the cheapest potential terrorist weapon. No one needs a money-laundering scheme to start a fire with gasoline. Moreover, it is unlikely that current security techniques would be able to prevent such attacks.
Analysts Mortimer Downey and Thomas Menzies, in an article entitled "Countering Terrorism In Transportation" in the periodical "Issues In Science And Technology," Summer 2002, discuss the difficulties of combating such terrorism in public-transportation networks.
"Understanding what deters terrorists is crucial for designing effective and efficient security systems, especially in a spread-out and heavily used transportation system," they wrote. "If you can't physically protect or eliminate every vulnerability, then it is important that you find ways to deter the act in the first place. Doing so will require a fair amount of creativity and innovation in security methods. This means employing tactics such as randomizing security screening, routinely setting traps, clandestine policing, and masking detection capabilities, that effectively create layers of uncertainty and inhibit terrorist activity through what have been called 'curtains of mystery'."
The Moscow Metro Bombing
For RFE/RL's coverage of issues related to terrorism, see "RFE/RL Organized Crime And Terrorism Watch"