Streets and Highways Code § 1701
ARTICLE 3. Extension of County Highways Through Cities
A copy of such resolution shall be forwarded to the governing body of the city within which is included any portion of the highway. Such governing body may consent to the establishment of such included portion as a part of the county highway. Upon the taking effect of an ordinance or resolution containing such consent, such portion of such highway shall become a county highway for one or more of the following purposes: acquisition of rights-of-way, construction, maintenance, improvement, or repair.