COLREG Rule 18: responsibilities between vessels

Rule 18 sets responsibilities between vessel types and statuses. It is a practical guide to who should keep clear in normal sighted encounters, not an absolute right-of-way ladder.

Power-driven and sailing vessels have specific keep-clear duties towards vessels engaged in fishing, vessels not under command (NUC), and vessels restricted in ability to manoeuvre (RAM). The exact Rule 18 wording and exceptions matter: vessels must also comply with the narrow-channel and traffic-separation rules, seaplanes and wing-in-ground craft have particular duties, and a vessel constrained by her draught is treated through the rule's avoid-impeding obligation rather than a simple universal ladder. Remember that a sailing vessel propelled by machinery is a power-driven vessel for the Rules.

First establish the encounter context. Rule 13 governs overtaking when vessels are in sight regardless of the categories involved; Rule 19 governs conduct when vessels are not in sight in restricted visibility. Even where Rule 18 allocates a keep-clear duty, Rules 2, 5, 7, 8 and 17 still require proper lookout, risk assessment and effective collision avoidance. No status gives a vessel an entitlement to hold course into danger.