Which sign warns you to slow down for a winding road?

The sign that warns you to slow down for a winding road is the yellow diamond with a squiggly line. This specific shape and color combination is universally recognized as a caution sign indicating that the road ahead has curves, encouraging drivers to reduce speed for safety. The squiggly line represents the twists and turns of the roadway, alerting drivers to be prepared for changing directions.

Other options do not convey this particular message. For example, the red circle typically indicates prohibitive actions or warnings, whereas the blue rectangle is often used for informational purposes, such as service signs. The green triangle usually indicates upcoming curves but lacks the specific warning of winding roads, making it less effective in this context.