What is the purpose of the 'No U-Turn' sign?

The purpose of the 'No U-Turn' sign is to restrict turning back in the opposite direction. This sign is implemented in areas where making a U-turn is deemed unsafe or may disrupt traffic flow. For instance, it might be placed at intersections where visibility is limited, where there are pedestrian crossings, or in locations with heavy traffic, to ensure the safety of both drivers and pedestrians. Adhering to this sign's instruction helps in maintaining a smooth and safe driving environment, preventing potentially hazardous maneuvers that could lead to accidents.

The other options relate to different traffic situations and rules, but do not accurately describe the specific function of the 'No U-Turn' sign.