Just as a stone sends waves rippling through a pond when it's dropped into the water, terrorist acts appear to impact society in a previously unknown way. A new study concludes that deadly attacks on innocent civilians also result in a dramatic increase in the number of fatal automobile accidents.

Researchers at Hebrew University in Jerusalem and Princeton University in New Jersey found that the number of fatal accidents had jumped by 35 percent on Israeli roads three days after terrorist attacks.

The investigators say they chose Israel to study because the country has a good system of record keeping, and it's experienced a growing number of terror attacks in recent years.

Study author Joshua Goldstein of Princeton University's Office of Population Research says Israel serves as a model of what's happening in many places around the world.

"We wanted to look for an everyday behavior, something that everybody did everyday, and see how that changed as a way of kind of taking the pulse of society in seeing how it reacted to the attacks," he said.

Researchers divided the accidents into light collisions, in which drivers didn't need to go to the hospital, serious, in which they did, and fatal. The only change noted by investigators the first day following an attack was a decrease in the number of light accidents, possibly because drivers were being more cautious. The average number of serious and fatal accidents remained the same.

But on the third day, researchers found the number of fatal accidents jumped by more than one third.

While the study was not designed to pinpoint a cause, Mr. Goldstein says it's possible the spike in lethal accidents resulted from a decrease in attention and an increase in hostility by drivers.

"Now, one explanation that has been proposed is that some of these deaths could be suicide; some people kill themselves by the way they drive [in] a behavior much like suicide. But we can't prove that. It's just consistent with other studies that have found that," he added.

The study on the effect of terrorism on driving appears in Proceedings of the National Academy of Sciences.