What is the maximum horizontal distance allowed between two masthead lights on a power-driven vessel?

The maximum horizontal distance allowed between two masthead lights on a power-driven vessel is 100 meters. This specification is outlined in the COLREGs, which establishes guidelines for the display of lights on vessels to ensure safe navigation and proper identification of different types of vessels at night or during restricted visibility conditions.

Having the masthead lights spaced appropriately enhances their visibility to other vessels, thereby reducing the risk of collisions. The 100-meter distance is based on practical considerations of maritime navigation, allowing for clear identification of the vessel's heading and status. This distance helps ensure that other mariners can accurately assess the size and type of the vessel from a sufficient distance, which is crucial for safe navigation in busy or congested waters.

While shorter distances may be permitted under specific conditions or for smaller vessels, the 100-meter standard represents a commonly accepted practice for larger power-driven vessels to maintain visibility standards under the regulations.