Entrance Ramps

First, unless you can look ahead and see that the ramp is clear, you shouldn't pass next to an entrance ramp, because the car you're passing might end up wanting to move over to get out of the way of entering traffic.

Passing on the right is bad, too, but for different reasons. If you're passing, you're going faster, and that makes it harder for entering traffic to figure out how to merge. Also, you're just setting yourself up for the frustration of having a slow-moving car come down the ramp and box you in.

Second, suppose you're driving along on an empty highway, and you see another car coming down an entrance ramp ahead of you; and suppose the timing is as bad as can be, so that if nothing changes you'll be exactly in the other car's way. If you're polite, you'll move over … and then you'll find yourself hovering next to another car. Normally, that would be bad, and you'd be obliged to cut it out, but here I think you should wait and see, because it often takes people a minute or two to figure out how fast they want to go. They don't literally figure anything out, of course, but they do sit around for a minute or two and then noticeably speed up or slow down. I'm not sure why that is … some psychological thing, I guess. Anyway, I think you should wait a minute and see what happens. If the other car speeds up or slows down, you can just move back over; if not, well, then you're hovering, and should cut it out.