COLREGS Rule 18 — Responsibilities Between Vessels

Rule Text

What it means on the water

• →Hierarchy (highest to lowest priority/give-way obligation): NUC > RAM > Constrained by Draft > Fishing > Sailing > Power-driven.
• →Power-driven vessel gives way to: NUC, RAM, fishing vessels, sailing vessels.
• →Sailing vessel gives way to: NUC, RAM, fishing vessels.
• →Fishing vessel gives way to: NUC, RAM.
• →CBD status (constrained by draft) is COLREGS only — not in Inland Rules.
• →Seaplanes keep well clear of all vessels in general.

Common exam mistakes

• ✗Placing CBD ahead of NUC — NUC is always at the top.
• ✗Forgetting that CBD is a COLREGS-only category (not in Inland Rules).
• ✗Thinking fishing vessels give way to sailing vessels — they do not; they are in the same tier as sailing vessels toward power-driven vessels only.
• ✗Forgetting that a sailing vessel using its engine is a power-driven vessel and loses its hierarchy advantage.

USCG exam questions — Rule 18

These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.

1. 1. Rule 2 of 72 COLREGS addresses responsibility. Which statement correctly reflects Rule 2?

   • A.The rules must be followed exactly as written regardless of circumstances
   • B.The owner and master are jointly liable for any collision regardless of compliance
   • C.Departing from the rules is permitted to avoid immediate danger when strict compliance would increase the risk✓
   • D.The stand-on vessel bears no responsibility once the give-way vessel has altered course

   Why: Rule 2(b) — the 'general prudential rule' — allows departure from the rules when necessary to avoid immediate danger. This reflects that seamanship and good judgment must override mechanical rule-following in extremis. Neither vessel is absolved of responsibility simply because the other vessel is the give-way.

2. 2. Two sailing vessels both have the wind on the same side. Under Rule 12, which is the give-way vessel?

   • A.The vessel to windward shall keep out of the way of the vessel to leeward✓
   • B.The vessel to leeward shall keep out of the way of the vessel to windward
   • C.The vessel on the starboard tack shall keep out of the way
   • D.The vessel that is making greater speed through the water

   Why: Rule 12(a)(ii) states that when both sailing vessels have the wind on the same side, the windward vessel keeps out of the way of the leeward vessel. The leeward vessel has less sea room to maneuver and the windward vessel can readily bear away.

3. 3. A vessel that is overtaking another begins to draw abeam and eventually moves ahead. At what point does the overtaking obligation end under Rule 13?

   • A.When the overtaking vessel is clearly past and well clear of the overtaken vessel✓
   • B.When the overtaken vessel can see the overtaking vessel's sidelights
   • C.When the overtaking vessel sounds two short blasts to indicate she is clear
   • D.As soon as the overtaking vessel crosses ahead of the overtaken vessel's bow

   Why: Rule 13(d) states that the overtaking vessel shall keep clear until she is finally past and clear. The obligation persists through the entire overtaking maneuver — there is no intermediate point where the give-way duty switches. The 'past and clear' standard is intentionally high to prevent premature assumption that the maneuver is complete.

4. 4. Under Rule 14(b), a head-on situation shall be deemed to exist when a vessel sees another vessel ahead and:

   • A.The other vessel's masthead lights are in line and her range lights can be seen
   • B.At night, she can see the masthead lights of the other vessel in a line or nearly in a line, or both sidelights✓
   • C.The bearing to the other vessel does not change over a 3-minute period
   • D.Both vessels are on courses within 10 degrees of each other

   Why: Rule 14(b) specifies the visual indicators of a head-on situation at night: masthead lights in line (or nearly in line) and/or both sidelights visible. This is the practical way mariners identify the head-on meeting without requiring precise course comparison.

5. 5. Rule 15 adds that, where possible, the give-way vessel in a crossing situation shall avoid:

   • A.Reducing speed, which could confuse the stand-on vessel
   • B.Crossing ahead of the other vessel✓
   • C.Altering course to starboard when the other vessel is on her starboard side
   • D.Sounding any signal that could be misinterpreted

   Why: Rule 15 states that the give-way vessel shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel. Passing astern is the preferred maneuver; crossing ahead risks collision if the give-way vessel underestimates the closing speed or the stand-on vessel maintains speed.

6. 6. Under Rule 17(a), the stand-on vessel in a crossing situation shall:

   • A.Immediately alter course to port to open the CPA
   • B.Immediately reduce speed to allow the give-way vessel more time
   • C.Maintain her course and speed✓
   • D.Sound five short blasts and then take independent action

   Why: Rule 17(a)(i) obliges the stand-on vessel to maintain course and speed. This predictability is essential — the give-way vessel plans its maneuver based on the stand-on vessel continuing unchanged. Unpredictable early action by the stand-on vessel can negate the give-way vessel's avoidance.

7. 7. Rule 17(c) states that a stand-on vessel taking action in accordance with Rule 17(a)(ii):

   • A.Becomes the give-way vessel for the remainder of the encounter
   • B.Shall not alter course to port for a vessel on her own port side✓
   • C.Must first reduce speed before altering course
   • D.Must sound the appropriate maneuvering signal before acting

   Why: Rule 17(c) prohibits the stand-on vessel from altering course to port for a vessel on her own port side when she decides to act under 17(a)(ii). Turning toward a give-way vessel approaching from the port bow would increase closing rate. Turning to starboard (away from the give-way vessel) is the correct action.

8. 8. A vessel engaged in fishing with nets (not trawling) is underway and making way. She encounters a power-driven vessel. Under Rule 18, which is correct?

   • A.The power-driven vessel must give way to the fishing vessel✓
   • B.The fishing vessel must give way to the power-driven vessel
   • C.Neither vessel has precedence — Rules 11-17 apply
   • D.The fishing vessel has precedence only if she is displaying the correct day shapes

   Why: Rule 18(a)(iii) requires a power-driven vessel to keep out of the way of a vessel engaged in fishing. A vessel engaged in fishing showing correct lights or shapes has this privilege regardless of size. However, a vessel displaying the fishing lights must actually be fishing — if she is underway with gear stowed, she loses the privilege.

Frequently asked questions

Which vessel has the highest priority under Rule 18?

A vessel not under command (NUC) has the highest priority — all other vessels must keep out of its way. The hierarchy from highest to lowest is: NUC, RAM, Constrained by Draft (COLREGS only), vessel engaged in fishing, sailing vessel, power-driven vessel underway.

Does a sailing vessel have to give way to a fishing vessel?

No. A sailing vessel does not give way to a vessel engaged in fishing. Rule 18 requires fishing vessels to keep out of the way of NUC and RAM vessels, but they have no expressed duty to give way to sailing vessels. However, all vessels retain the duty to avoid collision.

All COLREGS rules