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Rule 15: Crossing Situation (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 15 says that when two power-driven vessels are crossing with risk of collision, the vessel that has the other on her own starboard side keeps out of the way. If the circumstances allow, she should avoid crossing ahead of the other vessel. The vessel on the right stands on.

The rule text

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.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 15

What it means on the water

  • Look to your starboard side. If the other power-driven vessel is there, you're the give-way vessel.
  • At night you'd see her red (port) sidelight. Red means you give way.
  • Give-way action should be early and substantial (Rule 16), and passing astern of her is usually the cleanest choice because Rule 15 says to avoid crossing ahead.
  • The other vessel is the stand-on vessel and keeps her course and speed (Rule 17(a)(i)).
  • If the stand-on vessel does act under Rule 17(a)(ii), Rule 17(c) says she should not alter course to port for a vessel on her own port side, if the circumstances allow.

International vs Inland

Inland adds Rule 15(b): on the Great Lakes, Western Rivers, or water specified by the Secretary, a power-driven vessel crossing a river keeps out of the way of a power-driven vessel ascending or descending the river. Otherwise the same.

Common exam traps

  • Mixing up whose starboard side counts. It's the other vessel on your own starboard side.
  • Using Rule 15 for sailing vessels. Two sailing vessels use Rule 12; sail vs power uses Rule 18.
  • Missing the Inland river-crossing exception in Rule 15(b).

Try 3 questions on Rule 15

  1. A power-driven vessel is crossing from your starboard side with risk of collision. You are power-driven. What do you do?

    1. Stand on
    2. Keep out of the way
    3. Sound five short blasts and stand on
    4. Alter to port to cross ahead
    Show answer

    B. Keep out of the way Rule 15: the vessel with the other on her own starboard side keeps out of the way.

  2. At night you see only the red sidelight of a crossing power-driven vessel. Who gives way?

    1. You do
    2. She does
    3. Neither
    4. The larger vessel
    Show answer

    A. You do Seeing her red (port) light means she is on your starboard side, so you give way under Rule 15.

  3. On the Western Rivers (Inland), a power-driven vessel crossing the river meets one descending it. Who keeps out of the way?

    1. The descending vessel
    2. The crossing vessel
    3. The smaller vessel
    4. Neither
    Show answer

    B. The crossing vessel Inland Rule 15(b): the vessel crossing a river keeps out of the way of one ascending or descending.

Frequently asked questions

Who gives way in a crossing situation?

The power-driven vessel that has the other on her own starboard side (Rule 15).

Should the give-way vessel cross ahead?

Rule 15 says she shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.

Does Rule 15 apply to sailboats?

No. Rule 15 covers two power-driven vessels. Sailing vessels use Rule 12 between themselves and Rule 18 with power-driven vessels.

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