Warning Signs: Anticipate the Hazard
Warning signs alert you to a change in conditions ahead so you can adjust speed and position. In Arizona they are typically yellow diamonds with black symbols, with some exceptions: a circular yellow sign with an X means a railroad crossing ahead, and pentagon-shaped signs mark school zones and school crossings. Warning signs do not create a legal command by themselves, but ignoring one can still violate the basic speed law - you must drive at a speed reasonable for conditions.
Know the major symbol families: curve and turn signs (a curve arrow with a speed plate below is an advisory speed, not a legal limit), hill and downgrade signs, slippery-when-wet, lane-ends and merge, two-way traffic, divided highway begins or ends, deer and animal crossing, and intersection warnings such as a side road or a Y-intersection. Advisory speed plates are a classic trap: the yellow number is a recommended maximum for the curve, not a posted speed limit.
Other traps: assuming a warning sign means the hazard is at the sign rather than ahead; confusing "lane ends" with "added lane"; and treating a deer-crossing sign as a guarantee that animals appear only at that spot. Distance plates (such as "2 MILES") tell you how far the condition extends or begins.
Rule of thumb: warning signs buy you time - slow down and increase following distance before you reach the hazard. Worked example: you see a yellow diamond with a right-curve arrow and a yellow "35 MPH" plate. Your response is to reduce speed toward 35 mph before entering the curve and stay in your lane; you are not required to travel exactly 35, and the sign does not make 35 the legal limit for the road.