9/11's fatal road toll: terror attacks presaged rise in U.S. car deaths.

The crashes of four airplanes and the massive loss of life in the Sept. 11, 2001, terrorist attacks traumatized people throughout the nation. Tragically, in the last 3 months of that year, fear of flying revved up car use and caused a second toll of lives on U.S. roads, a new analysis suggests.

Compared with the average number of automotive fatalities for the same months from 1996 through 2000, an additional 353 people died in car crashes in October, November, and December of 2001, says psychologist Gerd Gigerenzer of the Max Planck Institute for Human Development in Berlin. Surplus road fatalities following the terrorist attacks thus exceeded the 266 fatalities on the four ill-fated aircraft.

According to Gigerenzer, people tend to avoid situations for which they feel "dread risk," a fear of many deaths occurring at once. For instance, many people refuse to fly in the wake of major airplane crashes, according to Gigerenzer. Activities in which deaths pile up more slowly but inexorably, such as driving an automobile, don't fuel dread risk, he says.

After 9/11, U.S. residents' responses to the dread risk associated with flying backfired, the German researcher concludes in an upcoming Psychological Science. Car travel increased as air travel declined, but flying remained far safer than driving (SN: 1/11/03, p. 20).

"The public needs to be better informed about psychological reactions to catastrophic events and the potential risk of avoiding certain risks," Gigerenzer says.

Psychologist David G. Myers of Hope College in Holland, Mich., made much the same point in December 2001, when he predicted that a terrorism-inspired boost in automobile use would lead to about 800 additional car-related deaths in 2002. Monthly data on 2002 road fatalities have not yet been released.

Excess car deaths attributable to 9/11 had already begun to accumulate by the time Myers made his prediction, Gigerenzer finds. Airline data confirm large drops in passenger miles for the last quarter of 2001. Monthly miles driven rose nearly 3 percent in October, November, and December, much greater increases than in any months earlier that year. Moreover, in the last 3 months of 2001, the largest traffic increases occurred on rural interstate highways, indicating that long-distance travel surged.

Gigerenzer also consulted federal data on fatal car crashes. The average number of deaths in each month of the year remained consistent from January 1996 through September 2001. Fatalities then substantially rose in the final 3 months of 2001.

Gigerenzer may have tapped into an extreme example of people's tendency to rely on emotional reactions to situations when estimating risk, remarks psychologist Paul Slovic of Decision Research, a nonprofit research corporation in Eugene, Ore. This mental shortcut often works well, but it causes people to overestimate the likelihood that especially frightening events will recur, Slovic proposes.

"It is perfectly normal to fear purposeful violence from those who hate us," Myers says, "but smart thinkers will also want to check their intuitive fears against the facts."