re: What % of drivers know that "drive right" is the law?

Predictable is a word too open to interpretation.

Now, If he got over when you were a quarter mile back, then it's a none issue even if you have to slow down a little at the tail end of his pass. In this case, to him, your speed is not predictable especially at a quarter mile. What is predictable is that his current speed needs to change or he needs to move over to pass he vehicle in front of him. His decision is based upon whether or not you coming from behind will over take him before he would over take that car in front of him... unfortunately that's not an exact science and people's depth perception is not perfect, especially when looking in a mirror. It's more important for drivers on the highway to spend more focus on what's in front than what's behind, though a good balance of both is necessary for good driving and to prevent him from cutting you off. Just like you from a quarter mile back can better tell that if he got over, you don't have a free lane to pass him yet, so if you don't change speeds then you will impact. Luckily from a quarter mile back you have plenty of time to adjust safely. Now if you're rapidly enclosing on him and he cuts you off from 50 to 100 feet, that's not safe. Everything in between is all open to everyone's best perception of the circumstances at the time.