I obey them. They’re most definitely not suggestions out here.
I’m in the greater Los Angeles area, where as people have pointed out they’re all over the place. I agree with blowero as to the reason that they’re there - I’ve read somewhere myself that “clumping” of incoming traffic is what they’re intended to prevent. My own personal experience is that they work, too.
Many (but by no means all) on-ramps here have two lanes: one for “carpools” (generally, multiple-occupant vehicles), and one for others. There’s typically a sign reading “Carpool lane does not stop,” giving that line free blow-through of the signal light.
But, it seems, this is simply too tempting for the more self-important solo drivers out there. It’s hardly rare for me to observe someone driving alone up the carpool lane so that they may skip the queue in the other lane.
Just the other day I was driving on the 605 freeway and I observed a CHP motorcycle officer sitting on the right shoulder, looking off to his right over the slope. I wondered what he was doing until I passed his location and realized that he was looking down at a light-controlled carpool/other onramp. I can only suppose that he was staking it out, waiting for someone driving alone to breeze through the carpool line. I doubt he had to wait long.
These things don’t operate like normal traffic lights. There is usually a sign saying “One car per lane each green,” or something similar (occasionally it’s two cars). When it flashes green, the front car in the line can go - the next guy has to wait. If you’re not off the line when it flashes back to red, you can still go if you were in front. No, the second guy can’t go if he tailgates the first dude and gets by the signal before it turns red again.
In keeping with this forum’s title: My Humble Opinion of those who feel these lights need not apply to them is rather low.
Full disclosure: I accidentally blew through one a few months ago. It was on the ramp I usually take to work, at an hour when the signal was usually not activated. It was also partially obscured by a bush, but I would have had time to react had I been paying attention rather than assuming it wouldn’t be on. I flashed by it, caught a bit of red in my peripheral vision, and thought, “Hey, was that thing on? Oooh…crap.” There were no flashing red & blue lights in my near future, so I decided luck was with me. I opted not to drive to the nearest CHP depot and turn myself in.