Everywhere I've driven in the US with HOV lanes, also has the restricted lane(s) separated from the unrestricted lanes by a single or double solid line and the lanes themselves have a diamond painted in them every X number of feet.

Even if you aren't able to read the entire sign, there are other clues that should alert you to the fact that you might not want to be in that lane.

The question of interest is not merely "is this an HOV lane" but "can I use it at this time" and "is there anything the sign says other than the usual stuff that I would need to know". You're supposed to read all road signs, and only after reading can you be sure that their information is redundant.

Yet HOV lanes can be minimum 2 people most of the time, minimum 4 people during certain hours. If you're in a car with 2 people, you want to know if you're allowed to use the HOV lane or not.

Well, "HOV 2+ ONLY" is the only part you actually need to read in the moment.

And helpfully those words are much much larger.

I will note that signs like that don't exist in my area.

It's admittedly (probably) not from Colorado, yeah. Though the important part you need to read is really the hours, since the other stuff doesn't tend to vary. Which they helpfully used a smaller font for, to make sure so you don't forget to squint at the most relevant part.

It's definitely distracting to have so much text, since you're still supposed to quickly read all of it, just in case it might say something other than what you expect. Not sure how that's supposed to work at 65+ mph.

good example, it just means one hopes that there are at least 3 subsequent of the same sign so one can read it in chunks (at least that's what i do)