Streets and Highways Code § 125

To notify the public that a state highway is closed or its use restricted, the department may:

(a) Erect suitable barriers or obstructions upon such highway.

(b) Post warnings and notices of the condition of any such highway.

(c) Post signs for the direction of traffic upon it, or to or upon any other highway or detour open to public travel.

(d) Place warning devices on such highway.

(e) Assign a flagman to warn, detour or direct traffic on such highway.