Which part of the COLREGs does NOT cover any rules about conduct?

Part D of the COLREGs focuses specifically on the conduct of vessels in restricted visibility and provides guidelines for how to navigate safely under those conditions. However, it does not contain specific rules about general conduct at sea, such as the responsibilities of vessels to avoid collisions in various scenarios.

In contrast, Part A establishes the general principles and definitions applicable to all vessels, which includes specific responsibilities for conduct. Part C addresses the conduct of vessels in restricted visibility and specific navigation rules, while Part E discusses additional provisions related to the conduct of fishing vessels and their communication protocols. Thus, Part D stands out as it primarily revolves around visibility concerns without detailing broader conduct rules applicable in other circumstances.