2005 Arizona Revised Statutes - Revised Statutes §12-820.03  Affirmative defense

Neither a public entity nor a public employee is liable for an injury arising out of a plan or design for construction or maintenance of or improvement to highways, roads, streets, bridges, or rights-of-way if the plan or design is prepared in conformance with generally accepted engineering or design standards in effect at the time of the preparation of the plan or design, provided, however, that reasonably adequate warning shall be given as to any unreasonably dangerous hazards which would allow the public to take suitable precautions.