Suppose the unthinkable happened, and terrorists struck New York or another big city with an atom bomb. What should people there do? The government has a surprising new message: Do not flee. Get inside any stable building and don’t come out till officials say it’s safe
Interesting fact from the article (emphasis mine):
Even staying in a car, the studies show, would reduce casualties by more than 50 percent; hunkering down in a basement would be better by far.