What type of sign is used to indicate that a road curves ahead?

The correct answer is that a warning sign is used to indicate that a road curves ahead. Warning signs are designed to alert drivers to potential hazards and changes in road conditions that may require them to adjust their speed or change their behavior. A sign indicating a curve ahead serves to inform drivers of the need to navigate the upcoming bend safely, helping to prevent accidents that could occur if they are not prepared for the change in the road trajectory.

Warning signs are typically yellow and feature symbols or diagrams that communicate specific hazards. In the case of a curve, the sign often includes a picture of a curve along with an advisory speed sign to guide drivers on how fast they should be going while negotiating the turn.

Other types of signs, such as regulatory signs, inform drivers of laws and regulations they must obey; information signs provide helpful details about services or directions without indicating any necessary changes in driving behavior; and guidance signs generally help direct drivers towards locations or provide distance information. These functions do not apply when indicating a road curve, hence making warning signs the correct choice for this situation.