[cjbprime]

They already do the first possibility.

The second and third wouldn't help, because they are strictly more work than the first, and the first wasn't done here even though it was available.

There will always be people who are too drunk or tired or uninterested to do your protocol, and those are the people most at risk who need it.

Something that might work is a recognizable LED light sign that goes on the roof, like a yellow cab has. It would be hard not to notice that this is missing, since it's visible from almost every angle. Then again, if you're not sober, there's really not much that can be relied on.