...like if the GPS glitches a little and decides you're on a feeder or surface road when you're actually on a freeway
I recall someone analyzing records from LexisNexis or similar (maybe in a news article or lawsuit?) and uncovering all kinds of instances where they were incorrectly labeled as speeding due to crossing a lower-limit road. Unfortunately I can't find the link.
It 100% happens repeatedly to me (my car has the little "tell you the speed limit" feature). It'll suddenly say the limit is 30 because the GPS thinks I'm on the feeder road nearby.
To account for such errors the limiter should probably set the limit to the highest of any road within ~50 m, with a possible exception for school zones that aren't immediately adjacent to highways.
I recall someone analyzing records from LexisNexis or similar (maybe in a news article or lawsuit?) and uncovering all kinds of instances where they were incorrectly labeled as speeding due to crossing a lower-limit road. Unfortunately I can't find the link.