Directional and other official signs authorized by section 28-7902, subsection A, paragraph 1 shall comply with rules that are adopted by the director, that are relative to the lighting, size, number, spacing and other requirements as appropriate to implement this article and that are not inconsistent with national standards as may be adopted by the United States secretary of transportation pursuant to 23 United States Code section 131(c).
A.R.S. § 28-7904