IALACOLREG
Academy

COLREG

Rule 15: Crossing Situation

When two power-driven vessels cross with risk of collision, the one with the other on starboard keeps out of her way and avoids crossing ahead if possible.

You · A
Decision 1 of 3

Two power-driven vessels in sight, with risk of collision. You are in A: who must keep out of the way?

How it applies

  1. WhenTwo power-driven vessels in sight of one another, on crossing courses, with risk of collision: the other's bearing does not change appreciably (Rule 7).
  2. Who gives wayThe one with the other on her starboard side. Act early and clearly (Rules 8 and 16): usually turn to starboard and pass astern. If the circumstances admit, do not cross ahead of her.
  3. And the otherKeeps her course and speed (Rule 17).
    1. If in doubt that the other is acting in time, she sounds at least five short and rapid blasts (Rule 34).
    2. Once it is apparent the other is not taking appropriate action, she may manoeuvre herself; if the circumstances admit, not to port for a vessel on her port side.
    3. If the give-way vessel alone can no longer avoid collision, she must act.

The full version

Practise Rule 15 in the Academy

Free: a preview of this unit with its key points. The whole unit is in the Exam Pass, once for 12 months.

What the Exam Pass adds

  • The live model: move the other vessel and see who keeps out of the way each time.
  • Four new cases with sketches: to port, a sailing vessel, overtaking and at night.
  • The path through Rules 15 to 17, with your progress saved.
Preview Rule 15 in the Academy

Practise with the free test 40 questions with explained answers · no sign-up

Before you apply Rule 15

Rule 15 is for two power-driven vessels in sight of one another, crossing. In these cases another rule decides, or adds to it:

  • The other is a sailing vessel under sailRule 18: the power-driven vessel keeps out of her way, on whichever side she is (unless the sailing vessel is overtaking you).
  • The other comes from more than 22.5° abaft your beamOvertaking (Rule 13): the overtaking vessel keeps clear, and stays the overtaking vessel even when she later draws onto your starboard side.
  • You meet ahead or nearly ahead on reciprocal coursesHead-on (Rule 14): both alter to starboard and pass port to port.
  • Restricted visibility and you are not in sight of one anotherIn fog, heavy rain or the like, when the vessels are not in sight of one another Rule 19 applies, not Rule 15: each avoids a close-quarters situation and, for a vessel forward of the beam, avoids turning to port (unless she is being overtaken).
  • In a narrow channel or a traffic separation schemeRule 15 still applies, and Rules 9 and 10 add to it: do not cross the channel if you impede a vessel that can navigate only within it, and cross a scheme as nearly at right angles as practicable.
  • The other is not under command, restricted in her ability to manoeuvre or fishingRule 18: the power-driven vessel keeps out of her way, even with her on the port side.

Frequent mistakes

  • Wrong: "If the other vessel is on my starboard side, I keep my course."

    Right: If you have the other vessel on your starboard side, you keep out of her way.

  • Wrong: "I may cross ahead if I get there first."

    Right: Avoid crossing ahead when the circumstances of the case admit it.

  • Wrong: "Rule 15 applies to every crossing between vessels."

    Right: It requires two power-driven vessels crossing so as to involve risk of collision.

More detail for the exam

The rule in plain words

Who gives way?
If two power-driven vessels are crossing with risk of collision, the one with the other on her starboard side keeps out of the way.
Which manoeuvre do you avoid?
If the circumstances admit, the vessel keeping out of the way avoids crossing ahead of the other.
How can you remember it?
Rule 15 uses the bearing from your vessel. Sidelight colour shows her aspect.

Exam keys

  1. "On her own starboard side" identifies the vessel that must keep out of the way: the one seeing the other there.
  2. When the question says "if the circumstances of the case admit", that condition qualifies avoiding crossing ahead.
  3. Do not merge "avoid crossing ahead" with "keep out of the way": the former is an added, conditional instruction.

How to read it

Read the sentence from the observing vessel: where is the other? If it is on starboard, that vessel keeps out of the way.

Treat "if the circumstances of the case admit" as a condition on avoiding crossing ahead, not permission to ignore the Rule.

Key points

  • Two power-driven vessels crossing with risk of collision.
  • Other vessel on starboard → you keep out of the way.
  • If circumstances admit → avoid crossing ahead.
  • Sidelight colour shows her aspect; determine her bearing from your vessel.

This rule's practice test is free in full, with no sign-up. The 10-question free limit applies to quizzes and mock exams.

Official text

IMO COLREG 1972 U.S. Coast Guard — International Navigation Rules (2024)

Full wording of the rule, reproduced from the official source below.

When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.
Source:

More rules in this Part

More resources

Reviewed by Ramon Curto, Nautical teacher at IECNPC · Last reviewed:

Frequently asked questions about COLREG Rule 15

Which vessel must keep out of the way in a crossing situation?

The vessel which has the other on her own starboard side shall keep out of the way. Rule 15 applies when two power-driven vessels are crossing so as to involve risk of collision: if the other vessel is on your starboard side, you give way.

May the give-way vessel cross ahead of the stand-on vessel?

No, not if it can be avoided: the give-way vessel shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel. She must choose early and substantial action to keep well clear under Rules 8 and 16. Passing astern may be appropriate, but Rule 15 does not prescribe a universal starboard turn.

Does the crossing rule apply to sailing vessels?

No. Rule 15 applies only to power-driven vessels that are in sight of one another and crossing so as to involve risk of collision.