Cal. Gov. Code § 66101

To preserve the effective traffic capacity and safety of the West Side Freeway, to maintain and enhance the present character of the landscape abutting the freeway, and to ensure compatible land use and development at and near interchanges along the route, the kind, intensity, and design of land use and development occurring at the freeway interchanges on the portion of the West Side Freeway designated in Section 66100 shall be regulated within highway interchange districts, which districts shall be established by each local jurisdiction traversed by the West Side Freeway in which is located any of the interchanges identified in this chapter.