(The following article by Sewell Chan was posted on the New York Times website on July 16.)
NEW YORK — After the Sept. 11 terror attacks, the federal government took immediate steps to secure airplanes. Cockpit doors were locked, passengers thoroughly searched.
But it has been harder to ease the fears of bus and subway passengers after the July 7 attacks on London’s mass transit system. The very virtues of mass transit – easy access, frequent service and central locations – make it vulnerable. From 1991 to 2001, 42 percent of all terrorist attacks worldwide occurred on trains or buses, according to a recent study by the Brookings Institution.
The United States mass transit system also lacks the aviation system’s built-in security: limited accessibility, a ticketing system that requires identification and a single governing agency, the Federal Aviation Administration. By contrast, the Federal Transit Administration has little say over security policies. That’s left to the country’s 6,000 mass transit agencies.
Money is another problem. Since Sept. 11, 2001, the federal government has appropriated $250 million for transit security, compared with $18.1 billion for aviation security.
Given the problems, what can transit systems do? What follows is a review of the latest in technology and tactics.
Bridges
Challenge Until recently, an attack on a bridge – outside of wartime – seemed almost beyond contemplation. But experts are concerned about long-span suspension bridges, not only because they are vital for interstate commerce, but because a bombed bridge is a potent, terrifying image and therefore a lure for terrorists.
Strategy After World War I, engineers argued that a bomb on the deck of a suspension bridge wasn’t much of a threat, because “the primary structures of a suspension bridge are the cables and the towers,” said Darl Rastorfer, the author of a book on Othmar H. Ammann, the noted bridge designer.
Bridges, like the Golden Gate in San Francisco, pictured right, were built with contingencies. “There is redundancy in the general design of a suspension bridge,” Mr. Rastorfer said. “So even if one primary suspension cable was compromised, there are backup cables that are designed to take extra load.”
After 9/11, patrols of bridges and the waterways under them have become far more common. On many bridges, some car trunks are searched, and trucks are restricted. Some toll plazas have nearly as many cameras and security guards as airports. Bridge operators, including the Metropolitan Transportation Authority in New York, have tightened security around anchorages, which secure the cables.
While a bridge attack would be terrifying, casualties may not be high. “Bridges are big, tough things,” said Rod Diridon Sr., director of the Mineta Transportation Institute at San Jose State University in California. “You’re not going to bring a bridge down with a knapsack of explosives, or even a truckful, unless it’s in a strategic, precise place.”
Trains
Challenge An attack on the subway system is much more than just an attack on a subway train. “What you have is terrorism as a form of urban warfare rather than as a symbolic gesture,” said Juliette N. Kayyem, a terrorism scholar at the Kennedy School of Government at Harvard University. “It causes mass havoc, economic disruption or uncertainty, and obviously casualties. But it also cuts to the core of what it means to live in an urban environment.”
Attacks have already occurred. In 1995, there was a sarin gas attack on the Tokyo subway, and the London subway system has been bombed many times by the Irish Republican Army. In 1997, New York police uncovered a plot to bomb a subway station.
Strategy After a series of accidents in the early 1990’s, rail operators posted better evacuation instructions and installed windows that could be easily popped out in an emergency, said Christopher A. Kozub, an associate director at the National Transit Institute, a federally supported training organization at Rutgers University.
Since the 1970’s, cameras in train stations and platforms have proliferated and become more advanced. Clunky black-and-white cameras are being replaced by sharper digital video recorders. And the Houston transit authority is testing on-board cameras that can wirelessly transmit live, high-resolution color images. Several agencies, including New Jersey Transit, are experimenting with “smart cameras” that will automatically alert the authorities when a suspicious package is left behind. The cameras are hooked up to computer software that uses algorithms to tell the difference between a person and a package.
Terminals
Challenge Few targets are more vulnerable than a crowded, centrally located train terminal. The damage in London could have been much worse, if the bombers had attacked Victoria or Paddington station instead.
“The bombers in London, if they had wanted to target more carefully, could have shut down the transportation system to a much greater degree,” said Magnus Ranstorp, director of the Center for the Study of Terrorism and Political Violence at the University of St. Andrews, in Scotland.
Strategy Much has already been done to protect Grand Central Terminal, right, which is believed to be the busiest train station in the world, with 700,000 people passing through it each weekday. After Sept. 11, 2001, the perimeter of the station was secured with concrete barriers, which will soon be replaced by metal bollards. Inside are three kinds of sensors that can detect biological or chemical agents. The most advanced sensor, called an Autonomous Pathogen Detection System, is designed to detect chemical agents and set off alarms at a nearby police control room. A ceiling camera, designed to look like the dome of a light fixture, allows police to observe victims of a chemical attack and, perhaps, to identify attackers.
Bruce Hoffman, a counterterrorism expert at the RAND Corporation, views train terminals as a likely target of any suicide attack. “Inherently, suicide terrorism is about killing people, wherever there are vulnerable targets and collections of people in fairly compact space,” he said.
Buses
Challenge Buses are particularly easy to attack, because they operate at street level, without any station to impede the attacker. Of the 9.5 billion public transit trips taken each year in the United States, buses account for 60 percent.
Strategy In Israel, many buses, right, have explosive detectors and drivers can quickly activate barriers that block a suspected bomber from entering the bus, said Mr. Hoffman of RAND.
Some Israeli buses have rear exit gates that swing open only from the inside, far right, making it tougher for a bomber to board. Bus drivers also have been trained to open the doors in an attack, which disperses both the force of the blast and any shrapnel.
But making a bus blastproof would be far too expensive, said Mr. Kozub of the National Transit Institute. And because buses must be operated in regular traffic, he said, they will always be vulnerable to roadside or car bombs.
A single bus attack is unlikely to cause structural damage or kill great numbers of people. In the West, “compared to the masses of people that are gathered together in underground in confined spaces, buses have been found to be a less desirable target,” said Mr. Diridon of the Mineta Transportation Institute.