What is one of the obligations of vessels under Rule 18 concerning CBD?

Under Rule 18 of the COLREGs, the key obligation of vessels concerning the conduct of vessels when navigating in the presence of vessels that are constrained by their draft (CBD) is to avoid impeding their safe passage. This rule establishes the responsibilities of various types of vessels with respect to the presence of others that may have limitations in their ability to navigate, such as those constrained by draft or operating under specific conditions.

When vessels are aware of others that are unable to maneuver as easily due to their physical characteristics, they are required to take actions that allow those vessels to navigate safely. This is essential for preventing collisions and ensuring smooth maritime traffic, especially in constrained waterways where deeper-draft vessels may not have the flexibility to change course or speed effectively.

While other options might appear relevant to general safety and navigation practice, the explicit requirement under Rule 18 focuses on the obligation to respect the safe passage of those vessels that are limited in their ability to maneuver, thereby emphasizing the importance of situational awareness and responsibility in maritime navigation.