Which light must be higher than the sidelights on vessels?

The all-round white light or masthead light must be higher than the sidelights on vessels because it serves as a primary navigation light, providing visibility for the entire vessel from all directions. This positioning ensures that the all-round white light is the most prominent signal, which is crucial for other vessels to identify the size and orientation of the boat from a distance.

The requirement for the all-round white light to be higher than the sidelights is part of the standardized navigation rules that aim to prevent collisions and enhance safety on the water. The sidelights, which include the red light (port side) and the green light (starboard side), are positioned on the sides of the vessel to indicate its direction and help other boaters understand which way the vessel is facing. However, the all-round white light provides an overarching signal for all vessels to see, hence its elevated position.

The sternlight is placed at the rear of the vessel and does not have the same requirement for elevation over the sidelights, as it primarily signals the vessel's presence and direction when viewed from behind.