Originally Posted by slide
You are dead bang wrong, here fellow. You are on a fixed roadway so the angles NEVER change. What varies is apparent SPEED.
If the apparent speed of the other is faster than you, then you will pass behind him. Slower and you will pass in front of him. If there is NO or little difference in apparent speed, you will CRASH.
I'm amazed you are still alive old timer but also wonder if others who you've advised are doing as well.
You managed to describe this in a way that was more confusing than the original. But you are describing (badly) the same thing. The first guy was right, he just didn't fully explain that the "angle" he was describing was the relative bearing of the other vehicle.
The technique described is called "Constant Bearing, Decreasing Range".
If you point your finger at the other guy and you don't have to move your arm to stay on him, then you're going to hit if nothing changes. If your arm moves towards the front of your bike, he's going to pass ahead of you. If your arm moves towards the back, he's going to pass behind you.
The only time this isn't true is if they are running parallel with you or going away (in which case who cares, you're not going to crash into them).