Mad Driver Disease

Mad drivers, they are everywhere and anyone. While this is true, why are they so mad? The DMV, try as they might, 'limits' who gets a drivers license (or do they). Written tests, driving tests, and eye tests are administered and passed. Why do they not test for selfishness or self-centered-ness (is that a word)? People get mad on the roads because drivers do not care what happens to the other guy. They are only concerned with what happens to themselves, and getting to where they are going as fast as possible.
'Back in the old days', drivers had a thing called courtesey for other drivers. They could merge, change lanes, and even stop at a stop light (or sign). Now most drivers think nothing of cutting you off, driving down the emergency lane, and running stop lights.
Do yourself a favor, leave early and take the back roads less traveled. If someone cuts you off, just smile and wave (just long enough for them to hit the car in front of them).