COLREGS Rule 15 — Crossing Situation

Rule Text

What it means on the water

• →The vessel with the other ship on her starboard side is the GIVE-WAY vessel.
• →The give-way vessel shall avoid crossing AHEAD of the stand-on vessel.
• →The preferred action for the give-way vessel is to alter course to starboard (turn right and pass astern).
• →Applies only to power-driven vessels — sailing vessels follow Rule 12, which has a different hierarchy.
• →The stand-on vessel is governed by Rule 17 (maintain course and speed; act if give-way fails).

Common exam mistakes

• ✗Thinking the vessel with the other on its PORT side is give-way — it is the one with the other on its STARBOARD side.
• ✗Applying Rule 15 to sailing vessels — it applies to power-driven vessels only.
• ✗Forgetting that crossing AHEAD is specifically what the give-way vessel must avoid.

USCG exam questions — Rule 15

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

1. 1. Under Rule 9, a vessel shall not cross a narrow channel if such crossing:

   • A.Would require more than 5 minutes to complete
   • B.Impedes the passage of a vessel which can only safely navigate within that channel✓
   • C.Takes place during periods of restricted visibility
   • D.Is made at right angles to the channel

   Why: Rule 9(d) prohibits crossing a narrow channel if doing so would impede a vessel that can only safely navigate within the channel. The crossing vessel bears the obligation to yield; the channel-bound vessel has right of way in this scenario. Time or angle of crossing are not the legal standard.

2. 2. A sailing vessel sees another sailing vessel to windward but cannot determine whether that vessel has the wind on the port or starboard side. Under Rule 12, the vessel to leeward shall:

   • A.Sound five short blasts and maintain course and speed
   • B.Keep out of the way of the vessel to windward✓
   • C.Assume the other vessel is on starboard tack and give way accordingly
   • D.Reduce speed until the windward vessel's tack can be determined

   Why: The keyed answer is correct: under Rule 12(a)(iii), if a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether that vessel has the wind on the port or starboard side, she shall keep out of the way of the other. This is a safety default for the leeward (port-tack) vessel, requiring her to give way to the windward vessel. (Note: Rule 12(b) is the separate definition of the "windward side" — the side opposite that on which the mainsail is carried — and does not govern this ambiguous-tack situation.)

3. 3. Two power-driven vessels are meeting on reciprocal or nearly reciprocal courses such that there is a risk of collision. Each vessel shall:

   • A.The vessel on the port side shall give way; the starboard vessel shall stand on
   • B.Alter course to port so as to pass on the port side of the other
   • C.Alter course to starboard so that each passes on the port side of the other✓
   • D.Reduce speed and wait for the other vessel to take action first

   Why: Rule 14(a) requires both vessels in a head-on situation to alter course to starboard so they pass port-to-port. This is a bilateral obligation — both act simultaneously. Altering to port would increase the closing rate on the collision course and is explicitly wrong.

4. 4. Two power-driven vessels are in a crossing situation so as to involve risk of collision. Under Rule 15, which vessel is the give-way vessel?

   • A.The vessel that is making the greater speed
   • B.The vessel that is smaller in length
   • C.The vessel which has the other on her starboard side✓
   • D.The vessel which has the other on her port side

   Why: Rule 15 requires the vessel that has the other on her starboard side to keep out of the way. Memory aid: the give-way vessel sees a red (port) light on the crossing vessel — a reminder to stop. Speed and size are irrelevant to this determination.

5. 5. 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.

6. 6. 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.

7. 7. You are the stand-on vessel in a crossing situation. The give-way vessel appears to be taking no action. You sound five or more short blasts. What are you signaling under Rule 34(d)?

   • A.That you are altering course to starboard
   • B.That you are operating astern propulsion
   • C.That you are in doubt whether sufficient action is being taken to avoid collision✓
   • D.That you are engaging in restricted maneuverability

   Why: Five or more short and rapid blasts is the doubt or danger signal of Rule 34(d). As the stand-on vessel, you use this when in doubt that the give-way vessel is taking sufficient action. The signal can be supplemented by at least five flashes. It does not authorize you to take any particular action — it is a warning, not a maneuver signal.

8. 8. Under 72 COLREGS, if a give-way vessel in a crossing situation sounds two short blasts before altering course to port, this is:

   • A.Correct — COLREGS requires the signal before the maneuver as a proposal
   • B.Correct — it signals intent to pass to starboard
   • C.An action signal announcing the course change to port that is already occurring✓
   • D.Incorrect — COLREGS forbids sound signals in crossing situations

   Why: Under 72 COLREGS, two short blasts are an action signal — they announce that the vessel IS altering course to port (not that she intends to). No agreement from the other vessel is required or expected under COLREGS, unlike the Inland intent-based system.

Frequently asked questions

Which vessel is the give-way vessel in a crossing situation?

The vessel that has the other vessel on her own starboard side is the give-way vessel. She must keep out of the way and should avoid crossing ahead of the stand-on vessel. The preferred action is to alter course to starboard and pass astern of the stand-on vessel.

What if the give-way vessel crosses ahead of the stand-on vessel?

Rule 15 specifically prohibits this — the give-way vessel shall avoid crossing ahead of the other vessel. If circumstances require passing ahead, Rule 8 principles apply: the action must be early, large, and positive, and must result in a safe passing distance.

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