What is the function of the yellow traffic light?

The function of a yellow traffic light is to indicate that the signal is about to change to red. This alert serves as a warning to drivers that they should prepare to stop if it is safe to do so. When a yellow light is illuminated, it means that the red light will follow shortly, providing a brief moment for drivers to react. This is essential for maintaining safe traffic flow and preventing accidents at intersections.

The other options described represent different traffic signals or situations. A yellow light does not indicate a safe time to cross as a traffic signal is designed primarily for vehicles, not pedestrians. While pedestrian crossings are typically associated with green lights for safety, the yellow light serves a different purpose. Additionally, yellow lights are not used specifically to signal pedestrian crossings or warn of construction zones, which are typically denoted by other signals or signs. Thus, the role of the yellow light is vital for informing drivers of the imminent change in traffic signals, helping to ensure safety on the road.