Cal. Sts. & High. Code § 954.5

(a) The board of supervisors may, by resolution, terminate the maintenance of any county highway if it finds that the highway is unnecessary for the public convenience.
(b) Evidence that a county highway is unnecessary for the public convenience shall be taken at a public hearing set in accordance with the procedures for vacation of a public street, highway, or service easement in Sections 8323 and 8324. Notice of the hearing shall be mailed to the owner of any property served by that portion of a county highway subject to the termination of maintenance. A county highway may be deemed unnecessary for the public convenience on the basis of any of the following:
1. (1) The county highway does not provide the primary access to occupied properties.
2. (2) Traffic on the county highway is intermittent and of low volume.
3. (3) The county highway is impassable for more than six months and there is no demand that it be reopened.
(c) A certified copy of the resolution terminating maintenance shall be recorded as provided in Section 8325.
(d) If the board of supervisors resumes maintenance of a county highway on which maintenance was terminated under this section, a notice of maintenance shall be recorded in the office of the county recorder.
(e) If a determination is made that maintenance is no longer necessary, the county shall post signs clearly visible from the traveled highway at each intersection of the highway for which maintenance is being terminated with a maintained highway indicating that the county no longer maintains the highway. The sign shall read as follows: “This road is not maintained. ____ County is not responsible for any loss or injury suffered by reason of its use.” The county shall provide adequate maintenance to ensure that the signs remain posted in the appropriate places and the message is legible for a period of one year. Once such action is taken and duly recorded and the required signs are posted, the county shall not be held liable for the death of or injury to a vehicle owner, operator, or passenger, or for damage to a vehicle or its contents, resulting from a dangerous condition on such highway.