Final answer:
A curve sign is used to warn drivers of curves where the recommended speed is lower than the posted speed limit. Drivers should decrease their speed to safely navigate the curve.
Step-by-step explanation:
A curve sign is used to warn of a curve where the recommended speed is less than the posted speed limit for the highway. This sign indicates that drivers need to decrease their speed to safely navigate the curve. For example, if the posted speed limit is 50 mph, but the curve sign indicates a recommended speed of 30 mph, drivers should slow down to 30 mph or below when approaching the curve.