From John Mueller, at Ohio State, an article (PDF) which discusses how does the risk of terrorism measure[s] up against everyday dangers. Good stuff.

University of Michigan transportation researchers Michael Sivak and Michael Flannagan, in an article last year in American Scientist, wrote that they determined there would have to be one set of September 11 crashes a month for the risks to balance out. More generally, they calculate that an American's chance of being killed in one nonstop airline flight is about one in 13 million (even taking the September 11 crashes into account). To reach that same level of risk when driving on America's safest roads — rural interstate highways — one would have to travel a mere 11.2 miles.

But don't forget, terrorism is a threat to the very existence of the country. Bad drivers are petty annoyances.