>> the law does not require such people already doing 65 or
>> so to exit the HOV lanes for people doing 90.

> Suppose you are in the HOV lane doing 65. Traffic in the #1 lane to
> your immediate right is doing 75. There is a car behind you who wishes
> to drive 75, but is being blocked by you. Does the law require you to
> leave the HOV lane?

There are two cases:

* If the HOV lane can only be entered/exited at certain places
(Southern California style), then it is a separate roadway and you're
not required to exit (although common decency requires it anyway if
you don't ever intend to speed up as the faster driver wants you to).

* If it can be entered/exited anywhere (Northern California style),
then it is entirely subject to the standard keep-right-except-to-pass
rule. (Which is the law pretty much everywhere, but unfortunately
obscure in places such as CA.)