20230203 18333500 1.0 TRUE Master Plan of Highways The Master Plan of Highways was originally developed by the County of Los Angeles Department of Public Works (DPW); it designates roadways in Los Angeles County by their planned capacity. Categories include major highway, secondary highway, limited secondary highway, parkway, and expressway. Source: County of Los Angeles DPW; last update: January 10, 2017 for removal of Limited Secondary Highway near Castaic along Sloan Canyon.