The District contemplates a roving emergency-alert system.

Emergency management, in these uncertain times, requires a certain flexibility. Destruction, experts say, could strike anywhere, in any form: germ attacks on the Metro, radioactive bombs at the White House, suicide bombers on the Mall. Add to the terrorist scenarios the region’s sudden propensity for tornadoes and flash flooding, and it’s hard to know where preparations should even begin.

Sounds like a job for a breakthrough technology. In a public question-and-answer session last month, D.C. Emergency Management Agency Director Peter LaPorte brought up the notion of an alarm system that could go anywhere: “portable sirens mounted on flatbed trucks.”

LaPorte says such a truck could be leased during anthrax remediation at the Brentwood post office, to warn neighbors if there were a release of chlorine dioxide gas or some other hazardous material. If the truck were a success, he says, the city might consider acquiring one for future emergencies.

What would District alert trucks look—or sound—like? An alert signal on wheels, industry experts say, is a formidable piece of equipment. “[You’re] not gonna put something like this in the back of a pickup,” says Tom Ellison, sales manager for Connecticut-based siren manufacturer Whelen Engineering Company Inc.

S.E.S. USA, a Kenmore, Wash.-based company, uses Whelen’s siren equipment to custom-build mobile sirens for clients including the military, fire departments, and manufacturers that use hazardous chemicals. By the time the gear has been mounted on carts, S.E.S. project manager Bill Flynn says, the full rigs are 9 feet long and 30 inches wide, and weigh 1,400 pounds. Those are the small ones: The trailer-mounted model is 22 feet by 8 feet, and it checks in at 5,500 pounds. (Flynn recommends using a truck with a payload capacity of at least 1 ton—which usually has enough hauling capacity to carry a trailer.)

Sirens can be set to a variety of sounds—a steady drone, an up-and-down wail like a firetruck’s, an intermittent whoop—to send different messages. And mobile equipment is also often capable of broadcasting pre-recorded safety messages and functioning as a PA system.

But the trucks would not be roaming the streets as they played, like Election Day sound trucks or the flatbeds that carry Dixieland bands. The siren signal carries farther if it comes from above ground level, Flynn explains. So once a cart or trailer has been driven to the right spot, it’s anchored with outriggers while the siren gets hoisted to a height where it will be effective. The carts have winch systems that go 24 feet up, and the trailers have hydraulic equipment that pushes 28 feet into the sky. Once in place, the sirens can be operated from a distance.

Why not just send out police cruisers to patrol the streets and warn the citizenry? A cop car’s PA system is merely a “glorified bullhorn,” says David Miller, president of SafetyCom Inc., of North Little Rock, Ark., which builds and supplies parts for trailer-mounted sirens. The PA system on SafetyCom’s more powerful rotating-siren models, he says, can project its pre-recorded announcements 5,200 feet—just under a mile—in all directions. (It could go farther, Ellison says, but the decibel level at the source would become unbearable.)

A mile radius may sound impressive, but even without the topography and buildings that may get in the way, it’s hardly going to cover the spread-out District. Warning of a nerve-gas attack at St. Albans, for instance, would reach only as far as Klingle Road. In the event of a subway emergency, a truck at Metro Center would not quite get its message to Union Station, three short stops away on the Red Line.

Proper warning of a big emergency, then, would require a fleet of trucks, spread out and planted around the city. Sort of like the Civil Defense siren network that the city used to rely on. The city’s CD sirens, built to herald the eruption of the Cold War into a hot one, went out of operation roughly when the Soviet Union did, according to the Emergency Management Agency. And even when they worked, they couldn’t play back recorded safety bulletins.

Still, in the event of another terrorist strike, the public would likely be able to tune in to CNN for information by the time a truck fleet was spread out and ready to broadcast its messages. In his initial mention of the trucks, LaPorte raised the prospect of using them to rouse residents in the middle of the night.

Nor would they come cheap. A single siren cart from S.E.S. USA would set the District back approximately $40,000, Flynn estimates; a trailer would be about twice that amount. “They’re pretty spendy items,” Flynn says. “It’s not something you’re going to find just anyone footing the bill for.”

SafetyCom usually doesn’t sell whole trailer-mounted rigs, leaving its customers to assemble the components themselves. But Miller says the company has a contract with Oklahoma City that gives the city the option of buying such an apparatus, for something in the neighborhood of $69,000 if the Oklahomans take the full options package.

In a city that doesn’t know what’s coming next, that investment may be worth considering. Activist Cleopatra Jones says that a portable siren is one of the ideas that has surfaced in discussions about community preparedness in the wake of last year’s anthrax and flooding emergencies.

D.C., Jones says, is “used to dealing with snow and ice—not water, anthrax, and things like that.” CP