Which shape indicates a warning sign?

A diamond shape is used for warning signs because it is easily recognizable and conveys caution to drivers about changes in the road conditions or potential hazards ahead. The bright yellow or orange color of these signs further enhances their visibility and alerts drivers to pay extra attention. This shape allows for quick identification of warnings compared to other shapes like circles, which are generally used for regulatory signs (such as speed limits), squares, which can indicate informational signs, and triangles, which often indicate yield signs. The diamond shape's unique design is intended specifically to capture the driver's attention and signal the need for vigilance in the driving environment.