What indicates that you should reduce speed when approaching a curve?

The presence of a curved arrow sign specifically indicates to drivers that there is a curve ahead in the roadway. This sign is designed to warn motorists to reduce their speed in anticipation of the change in direction. Approaching a curve at high speed can lead to loss of control, particularly if the curve is sharp or if there are adverse weather conditions that affect traction.

While other options like broken lines and solid lines serve different purposes, they do not provide the same explicit warning about the need to adjust speed for a curve. A broken line indicates that passing is allowed, while a solid line typically indicates that passing is not permitted. A stop sign signifies that a complete stop is required at an intersection, but does not relate specifically to reducing speed for a curve. Therefore, recognizing the curved arrow sign is crucial for safe driving when navigating turns in the roadway.