Right. Here the databases are wrong so the GPS data will indicate 25mph and the sign looks like a speed limit sign so posted sign identification will likely be tripped up (again, based on reports from Tesla owner friends and colleagues). So for 1/4 of a mile on a 50mph road cars that automatically enforce the speed limit will be screwing up.
That sounds pretty unique to me; I've done a few 1000+ mile road trips across the US and have never run into a sign that looks like a speed limit but isn't actually one. The closest thing would be a yellow advisory sign, but those don't look like speed limits.
(This sounds like the kind of thing you should report to either your state or county -- AFAIK every state maintains a DB of posted limits with geofences, and correcting them is generally a high priority for ticketing reasons.)
Do you have an example? Not that I don't believe you; it just seems nuts to me that any state would have a sign that looks almost exactly like a speed limit but that isn't one.
For the record: I've gone through the length of MA a couple of times (NY to Boston), and have never noticed these. But maybe that's because I thought they were all speed limits.
That road, Concord Ave, is posted as a 35 or 40 mph road for its length. (The MassDOT GIS database lists that first segment in Lexington as having a 40 mph speed limit, object_id = 395024.)
I believe a casual sign-reader could easily see the default sign and mistakenly conclude the speed limit on the pavement they are on is 25 mph. If I was stopped for 30 in the vicinity of any of the default limit signs I posted, I really, really like my chances to have it dismissed.
