California Vehicle Code definition of
Official traffic control device
CVC Section 440. An "official traffic control device" is any sign, signal,
marking, or device, consistent with Section 21400, placed or erected
by authority of a public body or official having jurisdiction, for
the purpose of regulating, warning, or guiding traffic, but does not
include islands, curbs, traffic barriers, speed humps, speed bumps,
or other roadway design features.