The addition of an extra digit to the current (3 digit) NXX numbering system. I would be located after the "third" digit yielding --> "+1 (Area Code) NXXX-XXXX" This identifiable digital is easy to implement such that all users would keep their phone numbers, allow telephone systems to redirect calls such as "businesses" to answering machines or silent, and give the general public to decline a specific category call.
It would be a low cost to the federal government since the responsibility to update software at the user end is the responsibility of the maker.
It would allow more users to the area code systems since the addition of an extra digit.
It would allow software makers to silent calls from businesses that are not on their contacts list, "if wanted by the user"