As one ATF explosives expert said, "The only true defense is to shut the road down so no one can come down there. Sedans, sport-utility vehicles, a Ryder truck, a large flatbed vehicle or a truck -- there's no sure-fire way to look at that vehicle and say, 'That's a large vehicle bomb.' " The expert spoke on condition of anonymity because of agency security rules.
Added Bouchard: "Distance is our friend."
A D.C. police officer finishes inspecting a truck near the IMF building in Northwest Washington. Last week's orange alert bulletin noted that "there is no standard type of vehicle associated with" a car bomb and urged special attention to limousines as well, which often get close access to buildings.
(Sarah L. Voisin -- The Washington Post)
For the U.S. government, blast walls, barricades and setbacks at sensitive buildings have become the last line of defense. The Pentagon, White House and Capitol increasingly resemble fortresses. Defensive measures costing hundreds of millions of dollars are proposed or underway at more than 20 facilities, and the government has adopted a 100-foot setback as a guideline for high-security new construction in the United States and overseas.
The problem is that hardening some locations might redirect terrorists to "softer" ones, including hotels, malls or stadiums, analysts said.
"You cannot secure all of the potential targets for the U.S. government or government employees in Washington, or New York City for that matter," said Ronald K. Noble, who was U.S. Treasury undersecretary when the Secret Service shut Pennsylvania Avenue in front of the White House in 1995 and is now secretary general of Interpol.
Michael Mason, assistant FBI director for the Washington field office, likened the sense of vulnerability to boxing in the dark against a terrorist with "night vision goggles. They know when they're going to attack, how they're going to attack and where they're going to strike," he said. "You reach out and think you have an elbow. You think you have a shoulder, but it takes time to put it all together to effectively strike back."
For four years in the 1990s at the White Sands Missile Range in New Mexico, government technicians wired vehicles with explosives and tracked the blasts' effects with high-speed cameras. In Florida and overseas, scientists conducted similar tests -- adding buildings to the destructive mix.
Dubbed "Dipole Might" and funded by the National Security Council, the tests mapped the flight of debris as small as a matchbook, crater patterns and even the street sign-bending effects of blasts. Those experiments have become the basis of U.S. truck bomb forensics, allowing investigators to identify the type and quantity of explosive from studying the effects of the blast.
But in 2000, the money ran out, and so did the tests, the ATF said. Agents say they need more. Based on the experience in Iraq and around the globe, the diversity of explosives has grown.
The desert tests reflect both the promise and the limits of the struggle to manage the threat. Some outside observers say other government efforts have not been creative or energetic enough.
"The administration has focused primarily on two areas. . . . One is aviation security, and the other is bioterrorism," said Benjamin, a former Clinton administration official and co-author of "The Age of Sacred Terror." "Truck bombs have been very far down the list."
In March, the Transportation Security Administration awarded a $19 million grant to American Trucking Associations to expand Highway Watch, a computerized instant-reporting network through which professional drivers and highway workers can report accidents, thefts, hazards and suspicious incidents nationwide.
Cited by TSA officials as a major initiative, it, too, was funded at half the $43 million the industry requested back in 2002.
"We are the point men. We are the Distant Early Warning line for the trucking security problem," said Jeff Beatty, security consultant to ATA, comparing the system to the nation's northernmost radar defense line during the Cold War to detect a Soviet nuclear attack.