What's the most dangerous "mistake" that you often witness drivers doing?

Hey you! When you make a turn from a multi-lane road onto another multi-lane road, do you stay in your own lane or do you just go into whatever lane your Tourette’s takes you? Well, huh?!? This illustrates what I’m talking about. (I found this on a thread on reddit.com)

If you do the one on the right, I just want to tell you that you make me very angry and you could possibly bang up your car or kill someone.

What else do bad drivers commonly do that will probably kill someone one day?

Discuss. And get angry! For safety.