Terror experts doing the math to assess risks
Almost two years later, security officials across the country are taking a more mathematical approach to guarding the homeland.
It's called "risk-based methodology," and it's a way of thinking about the unthinkable to best deploy limited funds and manpower.
The Washington State Ferries system is now using the risk-based approach to determine how to thwart potential terrorist attacks and comply with new Coast Guard regulations.
State emergency-management officials use a simple formula — "history plus judgment equals forecast" — to determine the probability of a wide range of hazards, from terrorist attacks to tsunamis, wildfires or an explosion at the Umatilla Chemical Depot in Oregon.
Seattle police won't comment on their risk-assessment methods, citing secrecy concerns.
But all the techniques reflect a conundrum: How do you determine the likelihood that a building, boat or some public icon will be attacked?
The answer, say terrorism experts, is you don't. Instead, without specific intelligence, most risk-assessment models assume a constant threat.
And while formulas can help planners determine how to protect certain assets, imagination still plays a vital part in trying to predict a terrorist's next move.
Risk management traces its roots to the insurance industry, which uses actuarial tables to determine the life expectancy of smokers and the proper auto rates for chronic traffic offenders.
At one point, some of those same techniques determined that Seattle was 20 times more likely to be the target of a terrorist attack than most other cities.
The New Jersey-based Insurance Services Office, one of the country's largest providers of insurance-policy information, used a sophisticated catastrophe-modeling program to help set rates for terrorism insurance.
The military has been doing risk assessments of its bases overseas for years.
After the 1996 bombing of the Khobar Tower military dormitory in Saudi Arabia left 19 U.S. service members dead, the Defense Department ordered vulnerability assessments on more than 500 bases around the globe.
That same year, Congress required the Federal Aviation Administration and FBI to conduct threat and vulnerability assessments at airports considered "high risk." Citing security concerns, a spokesman for Seattle-Tacoma International Airport would not comment on whether it participated.
The U.S. Department of Energy uses a Design Basis Threat program to protect nuclear sites; and the federal Department of Transportation's Research and Special Programs Administration has reviewed the vulnerability of the nation's highways, railways, pipelines and ports.
International oil companies also have used risk-based methodologies to secure overseas pipelines and offices.
In 1998, the General Accounting Office, the investigative arm of Congress, reported that the Defense Department's risk-based methodology included these levels of probability: frequent, probable, occasional, remote and improbable — "so unlikely it can be assumed occurrence may not be experienced."
But many of the assumptions behind that approach were rewritten after experts investigated the Oklahoma City bombing in 1995.
A disgruntled former soldier, Timothy McVeigh, was convicted of planting a truck bomb near the federal building and killing 168 people. McVeigh was executed in 2001.
From a risk-management perspective, the likelihood of a terrorist attack on that day at that location was practically zero, said Rod Propst, senior operations analyst with the Virginia-based Anser Institute for Homeland Security, a nonprofit research organization established a few months before the Sept. 11, 2001, terrorist attacks.
Propst has conducted vulnerability tests on a wide range of military bases and civilian structures.
A few years after the Oklahoma City bombing, he removed the idea of "likelihood" from all his statistical models.
"We don't use likelihood in risk-based methodology anymore," he said. "We assume there is a likelihood."
The events of Sept. 11 made government risk managers further rethink notions about likelihood and probability.
"What is the probability that multiple terrorists would be able to slip through (airport) security, overwhelm the flight crews and successfully pilot the planes?" asked Joe Myers, risk engineer at Coast Guard headquarters in Washington, D.C.
"If you start multiplying those one-in-a-million probabilities, you end up with a very small probability of it occurring. And yet we experienced it."
Soon after Sept. 11, the Coast Guard began devising new risk-assessment tools to deploy its cutters, planes and helicopters.
Details are classified, but federal documents and interviews provide clues as to which factors the service included in its risk-based methodology.
Lacking a specific threat, the models assumed likelihood was "fixed at a constant value. ... The baseline assumption was that terrorist cells were operating with unknown targets and methods of attack."
In other words, the Coast Guard assumed all vessels and ports were potential targets.
Myers said planners then looked at three factors: terrorist threats, the probability an attack would succeed, and the potential consequences if it did.
The State Department and CIA are responsible for tracking terrorists, so the Homeland Security Department — which oversees the Coast Guard — focused attention on how terrorists could hit the maritime industry.
Planners drew up a matrix of possible maritime targets such as cruise ships and oil rigs, and matched them with potential ways a terrorist could strike.
To determine the probability of a successful attack, the Coast Guard looked at various factors, including: accessibility (whether a potential target was easily reached by the public, such as a port near a city center) and vulnerability (ferries were considered more vulnerable than cruise ships because ferries sail on more predictable schedules).
The next step was deciding which type of vessel would cause the greatest impact if destroyed or damaged.
Myers said planners figured a bomb on a riverboat casino would have less effect than a bomb on a ferry, even if the loss of life were the same. A disruption of the nation's ferry service would cause far more chaos than a security crackdown on floating casinos, he said.
Other formulas use a dash of math, said Propst. He offered this equation: Pe = Pi x Pn.
To determine the usefulness of a given strategy, Pe is the probability of effectiveness, which equals Pi, the probability that the bad guy would be interrupted, multiplied by Pn, the probability the bad guy would actually be stopped.
Such formulas are used to devise specific counterterrorism strategies, said Propst.
For local ferry planners, the 2000 bombing of the USS Cole in Yemen, which killed 17 sailors, showed that vessels are conceivable targets.
But just how terrorists might strike in the Puget Sound area remains difficult to gauge.
Despite all the science, planners still try to put themselves in the shoes of a terrorist — using a screenwriter's kind of imagination to come up with possible attack scenarios, and planning the best responses.
Scott Davis, safety-systems manager at Washington State Ferries, said he currently is devising scenarios that are both credible and potentially devastating.
Despite the mathematical models and statistical tools, there still is a huge element of unpredictability in risk-based methodology.
"There's no magic science to it," Davis said. "It's just the best that you can do."
Alex Fryer: 206-464-8124 or afryer@seattletimes.com