In Black v. State, 116 Ariz. 234, 235, 568 P.2d 1132, 1133 (App. 1977), the plaintiff was injured when the van in which she was a passenger collided with a vehicle that had stalled on the slick roadway. State, county and city police had arrived approximately ten minutes before the collision. The injured passenger sued on the theory that the police officers at the scene negligently failed to warn approaching traffic of the dangerous situation. The trial court directed a verdict in favor of the defendants. The Black court affirmed, but did so based on the driver's uncontroverted testimony that the snowfall and slick road conditions - a danger known and obvious to all drivers in the vicinity - caused the accident, rather than a failure to warn. See id. at 238-39, 568 P.2d at 1136-37. Thus, the court implicitly held that, but for the lack of causation, the city could have been liable based on its police officers' alleged failure to warn of the road hazard.