Men/Women that learned to drive from school.

The most important lessons I learned about driving were how to be a considerate driver.

What I've observed over the years is women are absolutely the least considerate drivers on the road. They are the type of person that will pull forward and block an intersection, and stare straight ahead. They won't acknowledge you. They saw you wanting to merge into the main traffic flow, but pretend like they didn't.

They will camp the left lane with the mentality of, "I'm going the speed limit"! This is habitually a point of contention with my wife and I. I will explain, "The left lane is not for cruising. It's for passing." It doesn't matter what I say though. She still thinks the speed limit is some kind of sacred rule that obviates her from any sense of courtesy on the road.

Not giving adequate room after passing. This one bothers me greatly, and most offenders I see are female or young kids. This is clearly the result of bad parenting. If you pass someone, PASS them. Do not proceed to match their speed and coast 5 feet in front of them. It is the height of rudeness and creates an unsafe condition where one needn't exist.

Use a cruise control. This one is related to the previous complaint. All too often someone will pass and then slow down, then speed up, then slow down. For goodness' sake, use the damn cruise control. It's so annoying to be traveling a constant speed and then have to slow down, speed up, slow down, speed up. Then, after passing the person due to aforementioned annoyance; see them zoom ahead to perform the same ritual.

Not anticipating. Some of the worst drivers are the ones that apply a brake for seemingly no reason at all. Just let the engine slow the vehicle down. The person that is always changing lanes and changing speeds, because they seem to have no idea where they're going or how to get there is probably directly related to not having a proper instruction in driving etiquette.

Basically, anyone that didn't have a Dad with life experience teach them how to drive.