Final answer:
A yellow, diamond-shaped advisory sign typically warns you that the highest safe speed for an upcoming turn is 25 mph.
Step-by-step explanation:
The type of sign that warns you that the highest safe speed for the turn ahead is 25 mph is typically a yellow, diamond-shaped advisory sign. These signs are often placed before curves or turns in the road to indicate the recommended speed limit based on the road conditions and the ideal speed for safely navigating the turn. This recommended speed takes into account factors such as the tightness of the turn and the visibility of the road ahead, ensuring drivers can maintain control of their vehicle without relying solely on the friction between their tires and the road.