When must the Rules concerning lights be complied with?

The correct answer is that the rules concerning lights must be complied with from sunset to sunrise and in restricted visibility. This provision is crucial for maritime safety, as lights serve as a primary means of communication between vessels and are essential for preventing collisions.

During nighttime, the visibility of vessels can be significantly reduced, and the presence of navigational lights becomes vital for identifying other vessels' type, course, and distance. Similarly, in conditions of restricted visibility, such as fog, rain, or other weather-related issues, lights are critical for maintaining situational awareness and ensuring safe navigation.

The requirement does not extend only to nighttime or daylight hours, nor is it limited to coastal waters. It encompasses all waters where vessels operate, ensuring a standardized approach to safety on the water. This is rooted in the COLREGs, which aim to provide a framework for safe vessel operation regardless of the location or time of day.