IALACOLREG
15

Crossing Situation

When two power-driven vessels are crossing, the vessel which has the other on her starboard side shall keep out of the way.

Rule 15 governs crossing situations between power-driven vessels.

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.

The give-way vessel should preferably alter course to starboard to pass astern of the stand-on vessel. The key principle is: if the other vessel is on your starboard side, you give way.

STCW Bridge Watch Lens

1

Decide applicability before manoeuvring: Rules 4-10 apply in any visibility, Rules 11-18 only when vessels are in sight, and Rule 19 governs radar-only encounters in restricted visibility.

2

Build the traffic picture with sight, hearing, radar/ARPA and chart context. Do not let AIS or one isolated bearing replace systematic observation.

3

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

1

Identify the vessel types first, then the relative bearing, then whether one vessel is overtaking. Misclassifying the encounter is the usual exam failure.

2

If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.

Key Takeaways

1

Give way to vessels on YOUR starboard side

2

Avoid crossing ahead of the stand-on vessel

3

Preferably alter to starboard to pass astern

4

Only applies to power-driven vessels in sight of each other

Common Mistakes

Crossing ahead of the stand-on vessel when it can be avoided

Confusing which vessel has the other on starboard side

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