The FasTrak scanners above the lane flash the occupancy setting (1, 2, or 3+) on the driver's transponder. It's easy to observe cheating single-occupant vehicles because the flashed number is 3 (a toll-free rate).

For automated enforcement, there's prior art in red light camera systems that mail tickets/violations to the registered vehicle owner.

Yeah, but you pay the full fare with 1 person, half with 2 people, and it's free with 3+.

It's something that isn't straight obvious though. When I got there I also thought that people were just in violation of the people requirement.

I don't get the point of the occupancy reader if there's no hard-requirement of 3+ in the current zone. Maybe there are some stricter HOV-only lanes nowadays? I left the bay area in late 2023

They did start enforcing a bunch of lanes after COVID.

In Washington state, for one, I know that there used to be a phone number posted periodically for civilian reports of HOV violators. That's gone now with just a warning of the fine amounts.

Yeah and some blind (gender-TBD) Karen reported me on that when they couldn't see my kids sitting in the back seat.