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CONTACT: Dawn Levy, News Service: (650) 725-1944,

COMMENT: M. Elisabeth Paté-Cornell, Management Science and Engineering: (650) 725-1624,  

EDITORS: This release was written by science writing intern Jessica Ruvinsky.

Engineer's work helps government prioritize terror risks

Across the United States after Sept. 11, people speculated about the next target of terrorism. In upstate New York, they worried about the nuclear power plant. In rural Ohio, it was the water system. In Iowa, they were sure agro-terrorism was the next wave.

All of these things, of course, are possible. And that's the problem. How can we ever decide what to protect and where to look? The field of probabilistic risk assessment may help guide policymakers through the process.

"We are trying to set priorities given what we know," says M. Elisabeth Paté-Cornell, the Burt and Deedee McMurtry Professor in the School of Engineering, chair of the Department of Management Science and Engineering, and a member of the President's Foreign Intelligence Advisory Board.

"When we have to make allocation decisions -- because we're not infinitely rich, and days have only 24 hours, and we have, for example, limited intelligence resources -- the question is, where do we start?" Paté-Cornell and one of her graduate students, Seth Guikema, provide a possible starting point in the December 2002 issue of Military Operations Research.

The starting point for girding against terrorism should not be our newest fear or most familiar nightmare. It should be an objective as possible assessment of the relative risks. But there are a lot of things to consider. Information comes in from all over: the CIA, FBI, National Security Administration, Department of Defense, Customs Service, Coast Guard, worried citizens. The information is variably reliable. And it relates to every aspect of every possible threat. Paté-Cornell's model uses systems analysis, probability and even game theory to try to prioritize the most likely threats and most useful countermeasures.

The first unknown is the terrorists themselves. Who are they, and what are they after? In her paper, Paté-Cornell considers a broad spectrum of groups, all the way from al Qaeda to what she calls the "American disgruntled."

Every terrorist has a different point of view, and Paté-Cornell takes that into consideration. What is a particular group's or individual's goal? Symbolic targets may be attractive, but killing as many people as possible may be preferable. Is simply causing widespread panic good enough? Or maybe someone just wants to attack without spending a lot of money.

The target terrorists choose depends on their objective. One may attack infrastructure, like the water distribution system or an airport. Another may aim for individual structures, like a U.S. military facility in the Middle East or a neighborhood church. Or a bus stop. Or they may go after livestock.

Another variable is the kind of attack a group might choose. Their arsenal may include biological, chemical and nuclear weapons. They can make dirty bombs and hijack planes. Suicide bombing and cyber attacks are other options. An attack could come from anywhere -- trucks and cars, airplanes, boats.

And after the initial attack, there are residual consequences. If the power goes out, what happens to communications systems? If telecommunications fail, what happens to banking? Ripple effects can turn a tragedy into a disaster. A dirty bomb wouldn't affect a large geographic radius, but the panic induced in the population could cripple a city.

So, what's the most likely scenario? Paté-Cornell won't say. "Of course, when I publish a paper like that, I use only illustrative numbers. In real life, one will have to use numerical information that often comes out of classified sources and to update it frequently."

Decision makers, like the rest of us, are unduly influenced by their own experience. The framework Paté-Cornell provides may help them decide more objectively where to put society's time and money.


Jessica Ruvinsky is a science writing intern at the Stanford News Service.


By Jessica Ruvinsky

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