Day Skipper theory guide · IRPCS
Day Skipper COLREGs: head-on, crossing and overtaking
The Collision Regulations are easier to apply when you name the encounter before choosing an action. Head-on, crossing and overtaking situations have different rules, and each starts with a proper lookout and an assessment of collision risk.
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Head-on: both act
When two power-driven vessels meet head-on or nearly head-on with a risk of collision, each alters course to starboard so they pass port side to port side. If in doubt whether the situation is head-on, treat it as such.
Crossing: check your starboard side
When two power-driven vessels are crossing with a risk of collision, the one with the other on her starboard side keeps out of the way and, if circumstances allow, avoids crossing ahead.
Overtaking takes precedence
A vessel overtaking another keeps out of the way until finally past and clear. This applies even when a simple sail-versus-power shortcut might suggest otherwise.
Worked example: two power-driven vessels head-on
You see another power-driven vessel ahead on a reciprocal course. The bearing remains steady and the range is closing. Treat the situation as a risk of collision. Both vessels should make an early, clear alteration to starboard and pass on each other's port side. Keep monitoring; the rule does not remove either vessel's duty to avoid a collision.
Identify the encounter, assess risk, then make the required action clear and early.
A common mistake
Assuming a power-driven vessel always keeps clear of a sailing vessel. An overtaking sailing vessel must keep clear of the vessel she is passing. Rule 13 applies to every overtaking vessel.
Try three questions
These are independent practice questions. Read the answer and explanation after making your choice.
01Two power-driven vessels are meeting head-on. What action should each take?
Answer: Both alter course to starboard so each passes on the port side of the other
Rule 14: when two power-driven vessels meet head-on, each must alter course to starboard so they pass on each other's port side.
02A power-driven vessel is overtaking a sailing vessel from astern. Which vessel must keep clear?
Answer: The overtaking vessel, in this case the power-driven one
Rule 13 overrides others: any vessel overtaking another must keep out of the way of the vessel being overtaken, regardless of propulsion. Here that is the power-driven vessel.
03Two power-driven vessels are crossing. The other vessel is on your starboard side. What must you do?
Answer: Give way and, if possible, avoid crossing ahead
Rule 15 makes the vessel that has the other on her own starboard side the give-way vessel. She should avoid crossing ahead if circumstances allow.
Sources and further reading
Examples checked against these primary sources on 27 September 2026. Check the latest editions before using any rule or calculation afloat.
- IMO overview of the COLREGs and Rules 13–17
- International Collision Regulations, official UK treaty text
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