On a power-driven vessel of 20m or more in length, what are the requirements for the positioning of masthead lights?

Masthead lights on power-driven vessels are critical for ensuring visibility and safe navigation during nighttime or low-visibility conditions. For a power-driven vessel that is 20 meters or more in length, the correct positioning requirement is that the masthead lights should be located at least 4 meters above the hull. This elevation helps to ensure that the lights are visible at a sufficient distance from other vessels and reduces the chance of obstruction by the vessel itself or nearby structures.

By positioning the masthead lights at this height, the vessel enhances its safety by making it recognizable to other waterway users. This is particularly important in congested waterways where multiple vessels operate close to one another. The elevated position of the lights also contributes to compliance with the COLREGs, which aim to prevent collisions and promote safe navigation.

In contrast, while it is indeed important for the masthead lights to be visible from both fore and aft, the specific requirement regarding their elevation is what makes the correct answer clear. The other choices do not align with the standardized regulations and requirements specified by the COLREGs concerning the operational characteristics and visibility of masthead lights.