What is the light requirement for power-driven vessels when underway?

The light requirement for power-driven vessels when underway is to display either an all-round white light or both a masthead light and a sternlight. This requirement ensures that the vessel is visible to others, particularly at night or during low visibility conditions.

The all-round white light is typically used for vessels that are smaller and may not have the space to install multiple lights, while the combination of a masthead light and a sternlight is common on larger vessels. The masthead light indicates the presence of the vessel and its direction of travel, while the sternlight provides visibility from behind, which is critical for preventing collisions.

These lighting requirements are part of the navigation rules designed to enhance safety on the water by allowing other boaters to clearly see and identify the presence and movement of power-driven vessels.