Although it appears in the 1985 Rand McNally atlas, it was withdrawn in 1977 or 1978. Robert A. Gurco, Director, Oregon Dept. of Public Works, testimony before Congress, May 1977 4. Faigin, Daniel 5. California Department of Transportation, November 1984. Posting to misc.transport.road, Jan 26, 2001.
Unnamed sources are either maps or personal experience.