Facing Facts in America

In America, subway bombs have been around longer than parking meters. Back when terrorists were called "radicals," in 1927, two explosions blasted through two midtown New York City stations late one August night, injuring 12. The bombs went off 10 minutes apart; one was strong enough to rip open the sidewalk on the street above. The city lunged into action. All 14,000 police officers were put on bomb duty to protect the city's water supply and public buildings, reported a New YorkTimes article from the time. Scores of New Yorkers carrying bundles were stopped and searched.

Last week, when London's transit system was wracked by four bombs, New York and other U.S. cities responded again with a mighty show of force. The Coast Guard escorted Staten Island ferryboats. The chief of the New York City police department promised there would be an officer on every rush hour subway train "for the foreseeable future." In Washington, cops clutching MP5 submachine guns strode through subway cars, and Capitol police searched tour buses.

The display was appreciated by many, but some found it hard not to wonder what will happen after the police go back to their day jobs. On TV, the usual cast of security experts roundly lamented insufficient funds for mass-transit security. Senator Joseph Biden of Delaware vowed to introduce a bill that would add $1.1 billion in new money and "make everybody stand up and be counted on it, goddammit." But without pausing for breath, everyone agreed there is really no way to prevent an attack from happening here. "Surface transportation is a killing ground," says Brian Michael Jenkins, a terrorism expert with the Rand Corp.

The blasts in London provided a disheartening lesson: crude bomb attacks can kill dozens, even with 6,000 cameras in the subway system and a populace taught by I.R.A. violence to report suspicious bags. But just because Americans can't prevent all bombings doesn't mean they should do nothing--or everything, in feverish, sporadic security binges. "We should all take a deep breath," says Stephen Flynn, a homeland-security expert at the Council on Foreign Relations. "There is an ongoing threat, and we need a sustained level of involvement."

Since the 1995 sarin-gas attacks in the Tokyo subway and the 2004 train bombings in Madrid, some U.S. cities have quietly made smart improvements to their transit systems. Hundreds of police are now equipped with handheld radiation detectors. They do flag the occasional chemotherapy patient, leading to at least a couple of unfortunate strip searches in New York City, but that means the devices are working.

At least 15 Washington stations also have chemical sensors. That leaves some 30 stations unprotected, and the sensors are still not perfect. But they are a good--and expensive--part of a larger surveillance strategy. If a sensor goes off, Metro officials check out the platform using closed-circuit video. They scan for odd packages or riders showing signs of illness. The idea is to identify a problem--fast--so evacuation can begin. That's because while a train bombing is bad, a biological, chemical or radiation attack on a train is an epidemic snaking through a city via a web of underground tunnels.