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OR and Suicide Bombs

This past weekend, the NY Times Magazine in its annual Ideas issue reports on Ed Kaplan’s work with Moshe Kress on damage done by suicide bombers. Here is an excerpt:

Even if you manage to detect a suicide bomber, what do you do next? This question was taken up by Edward H. Kaplan, a professor of public health at Yale, in a paper he published in July, written with Moshe Kress of the Naval Postgraduate School in Monterey, Calif. Kaplan and Kress investigated the physics of a belt-bomb blast and reached some unexpected conclusions. It turns out that very few people are killed by the concussive force of a suicide explosion; the deadly weapon is in fact the shrapnel – the ball bearings, nails or pieces of metal that the attacker attaches to the outside of his bomb. The explosions, though, are usually not powerful enough to send these projectiles all the way through a human body, which means that if your view of a suicide bomber is entirely obscured by other people at the moment of detonation, you are much more likely to escape serious injury. Because of the geometry of crowds, Kaplan found, a belt bomb set off in a heavily populated room will actually yield fewer casualties than one set off in a more sparsely populated area; the unlucky few nearest to the bomb will absorb all of its force.

The authors used these calculations to question some assumptions about what authorities should do if they detect a bomber. The International Association of Chiefs of Police issued guidelines this year suggesting that police officers who find a bomber in a crowd should fire shots into the air to cause people near the bomber to scatter or hit the deck. But Kaplan’s calculations demonstrate that in many cases, this would make things worse – as a packed crowd ran away from a bomber or dropped to the ground, the circle of potential victims around him would get wider and thus more populous, and more lives could be lost.

Amazing what a little OR will teach you!