The northern portion is also part of the California Freeway and Expressway System, as is the piece south of SR 12 near Rio Vista, though, of the latter, only the southernmost piece in Antioch is built to freeway standards. Both pieces are also part of the National Highway System,</ref> a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. The entire southern portion, from SR 4 to Sacramento, is eligible to be included in the State Scenic Highway System, and is officially designated as a scenic highway by the California Department of Transportation, meaning that it is a substantial section of highway passing through a "memorable landscape" with no "visual intrusions", where the potential designation has gained popular favor with the community.