I'm still curious about street signs.

Can any self driving car read parking signs because it's not like there is some API for when/where you can park or drop passengers off.

Waymo for one definitely reads signs, but I'm not sure about those. Lots are written in ways that the average adult human can't decipher.

I kid you not - “No parking Mon Tues and Thurs. Every Month” is a real sign. I'm yet to figure out what that means. Then there are the slightly confusing ones with conflicting messages which you learn to decipher with experience. Placement of signs (esp one-way) are not consistent or does not take into account and driving cars - how will a car exiting a garage or a highway know if it's one-way or no? Definitely not without a mapping software.

As someone who had to relearn the rules of the road for a new country - there is a lot that's unsaid.

I wouldn't be surprised if something like that existed now or in the near future. There are APIs for speed limit, it would make sense to have them for other traffic rules as well.

My naive view is that a simple RFID standardization would solve that.

Together with some regulations, of course. Though, this already has to be regulated. Not just anyone can put up a "only park during certain times" sign. (Right?)

Sure, put up a sign "do not park if moon full, no red cars at any time", on your own property. This only differs from the regulated road parking by attributes that are not visible on the ground (ownership).

But worse: RFID makes for duplicate signage. What if the visible and data signage differ?

For the last part: If the cars, for the most part, actually are able to read signs (which they should), the RFID would serve as additional security.

And in this case, any discrepancy would be reported back by any car passing by, so the error could be corrected quickly.

If they differ, then there will be regulation on which applies. No different than current practices. Usually happens if there are two languages.