Around here (Boston) there are many roads with both a name and a number. Route 16 is the Mystic Valley Parkway, and then later on that splits off and 16 is the Alewife Brook Parkway. Or, Route 60 is also High Street, at least by us. For these two think we use the number a bit more, but the name is also used. Other roads, like Route 2 are called that in some sections but not others (no one would call Memorial Drive "Route 2"). Even the interstates have names that no one would use: Route 128 is the "Yankee Division Highway", but everyone says 128 (or maybe 95). And some interstates have names people do use: the Mass Pike (Massachusetts Turnpike) can be called "90" but generally isn't.

Overall, this is complicated and it's not surprising to me that it's hard to get a computer to do the right thing.