Comment by tgb

There are already non-self-driving cars that get speed limits from signs. I’ve seen that feature in a Honda for example. I imagine you’d have multiple sources like a max speed for that type of road as a fallback. And you need to read speed limit signage due to temporary limits. There’s also variable speed limit roads near me now and so you have to read those electronic signs unless the database is updated very often (though no humans seem to obey those limits).