Rule 18: Responsibilities between vessels
Establishes the encounter hierarchy between vessel categories, with important exceptions.
Detailed Explanation
Except where Rules 9, 10 and 13 apply differently:
(a) Power-driven underway keeps clear of: (i) NUC, (ii) RAM, (iii) fishing, (iv) sailing.
(b) Sailing underway keeps clear of: (i) NUC, (ii) RAM, (iii) fishing.
(c) Fishing underway keeps clear, so far as possible, of: (i) NUC, (ii) RAM.
(d)(i) Any vessel other than NUC/RAM should, if circumstances admit, avoid impeding safe passage of a CBD vessel displaying Rule 28 signals.
(d)(ii) CBD vessel must navigate with particular caution.
(e) Seaplane on water should keep well clear and avoid impeding; if risk exists, comply with Part B.
(f)(i) WIG craft taking off/landing/near-surface flight must keep well clear and avoid impeding.
(f)(ii) WIG craft operating on water surface follows Part B as a power-driven vessel.
Key Points
- Hierarchy: NUC > RAM > CBD > Fishing > Sailing > Power
- Power-driven vessels give way to all restricted categories
- CBD must avoid impeding safe passage of constrained vessels
- Hierarchy does not override narrow channel or TSS rules
Examples
- Your power-driven cargo ship encounters a vessel engaged in trawling. Under Rule 18(a)(iii), you keep clear of the fishing vessel because power-driven vessels give way to vessels engaged in fishing.
- A sailing yacht sees a vessel displaying two red all-round lights in a vertical line (NUC). Under Rule 18(b), the sailing vessel keeps clear of the NUC vessel.
- A VLCC displaying CBD signals (three red all-round lights and a cylinder) is transiting a channel. Under Rule 18(d), all other vessels shall avoid impeding the safe passage of a vessel constrained by her draught.
Common Mistakes
- Placing 'constrained by draught' (CBD) at the same level as NUC or RAM in the hierarchy when CBD is only entitled to not be impeded.
- Forgetting that a vessel engaged in fishing loses its priority when it is not actually fishing.
- Assuming a sailing vessel always has priority over a power-driven vessel, ignoring that sailing must give way to NUC, RAM, and fishing.