Cal. VEH § 21352

The Department of Transportation may erect stop signs at any entrance to any state highway and whenever the department determines that it is necessary for the public safety and the orderly and efficient use of the highways by the public, the department may erect and maintain, or cause to be erected and maintained, on any state highway any traffic control signal or any official traffic control device regulating or prohibiting the turning of vehicles upon the highway, allocating or restricting the use of specified lanes or portions of the highway by moving vehicular traffic, establishing crosswalks at or between intersections, or restricting use of the right-of-way by the public for other than highway purposes.