I saw this excellent Atlantic article, on the over-signage on American roadways, over at Fark. The author that by trying to make roads safer, the uber-signage and uber-"law-ing" of american roads has made them more dangerous.
Economists and ecologists sometimes speak of the “tragedy of the commons”—the way rational individual actions can collectively reduce the common good when resources are limited. How this applies to traffic safety may not be obvious. It’s easy to understand that although it pays the selfish herdsman to add one more sheep to common grazing land, the result may be overgrazing, and less for everyone. But what is the limited resource, the commons, in the case of driving? It’s attention. Attending to a sign competes with attending to the road. The more you look for signs, for police, and at your speedometer, the less attentive you will be to traffic conditions. The limits on attention are much more severe than most people imagine. And it takes only a momentary lapse, at the wrong time, to cause a serious accident.
Like they say, read the whole thing.