A.R.S. § 28-643: Local traffic control devices

Local authorities in their respective jurisdictions shall place and maintain the traffic control devices on highways under their jurisdiction as they deem necessary to indicate and to carry out this chapter or local traffic ordinances or to regulate, warn or guide traffic. All traffic control devices erected shall conform to the manual and specifications prescribed in section 28-641. The manual shall include the specification that the yellow light duration must be at least three seconds.