The status quo is "a large number of drivers will recognize that the intersection should probably have one and at least exercise some caution".

It should be able to program a self-driving car with a) a database of known intersections and their conditions as a fallback and b) to evaluate the conditions of an upcoming intersection for safety even without the requisite signage.

I'd suspect they do that already - based on what I've read they're not relying entirely on signage and the lidar is looking for potential hazards. I'd suspect it act similarly to a human in that situation.

Maybe it'd run it if there's no one else around, but a human probably would too in that case.

I would think a self driving car would have access to Waze in almost real time.

Maybe a large number of drivers would know, but that’s pure guessing. Could be a larger number of drivers wouldn’t know.

A while back, one of the four-way stops in our area got turned into a two-way stop. It took months for folks to stop treating it as a four-way, despite "new traffic pattern" signs.

Another imperfect analogy is power outages and stop lights. For the most part, it doesn't result in full-speed collisions; instead, folks treat it as a stop sign.

Self-driving cars are going to need a "huh, that doesn't look right..." system. Detecting missing/defaced/misleading signs should be a part of it.

> instead, folks treat it as a stop sign.

That's what you're supposed to do. In some cases, the traffic lights fail to a mode where one direction is blinking red, which is treated like a stop sign, and the other is blinking yellow, which is treated sort of like a yield sign (i.e., proceed, but with caution).

I believe the law (and common sense) states that if the traffic light it out, you treat it like a 4-way stop sign intersection.