I wonder if its a cultural thing. In my area of Not-California, roads will often have a local municipal name, but also be a county highway. For a while, navigation was unaware of this and would tell you "turn on highway 48" while driving downtown. As a driver, you go "wtf is highway 48". YIou have to zoom all the way in on the map to see that its Bank Street. Now it usually says "Bank Street", but will only display the 48 on the map. Very frustrating.