Module 5 - COLREGs
Stand-On and Give-Way Obligations
What you will learn
Distinguish the give-way vessel's early duty from the stand-on vessel's staged may-act and must-act responsibilities without waiting until collision is inevitable.
Stand-on means predictable initial conduct, not passive entitlement. Both vessels keep assessing risk, and Rule 17 deliberately changes the stand-on vessel's options as the give-way failure develops.
Rule 16 requires every vessel directed to keep out of the way, so far as possible, to take early and substantial action to keep well clear. The manoeuvre must meet Rule 8 and remain understandable to the stand-on vessel; a token course change followed by uncertainty does not discharge the duty.
Under Rule 17(a)(i), the stand-on vessel initially keeps course and speed, preserving a predictable reference for the give-way vessel. Rule 17(a)(ii) then says she may take avoiding action by her manoeuvre alone as soon as it becomes apparent that the vessel required to keep out of the way is not taking appropriate action.
Rule 17(b) is the later must-act stage: when the vessels are so close that collision cannot be avoided by the give-way vessel's action alone, the stand-on vessel shall take the action that will best aid collision avoidance. For two power-driven vessels in a crossing situation, a stand-on vessel acting under 17(a)(ii) should, if circumstances admit, not alter to port for a vessel on her own port side.
The boundary is judgement, not a fixed distance. Repeated bearings, range, closure, sea room and the other vessel's apparent action must be monitored continuously. Sound or light warning signals and speed reduction may be relevant, but none replaces the manoeuvre required to avoid collision.
Recognise the two Rule 17 thresholds
A motor yacht is stand-on in a crossing situation. The give-way vessel holds a steady bearing and shows no obvious alteration as range closes.
1. Stay predictable
Initially keep course and speed while retaking bearings and preparing an escape action.
2. Use the may-act stage
When the failure to take appropriate action becomes apparent, take a clear safe manoeuvre rather than preserving status for its own sake.
3. Do not miss must-act
If give-way action alone can no longer avoid collision, take whatever action will best aid avoidance and continue monitoring.
Sense check: A Rule 17 plan should name both the earlier permission to act and the later obligation; 'hold course at all costs' fails the rule.
Common mistake or limitation
- The stand-on vessel does not immediately manoeuvre in every crossing, because predictable course and speed initially enable the give-way action.
- The stand-on vessel does not wait for impact: the may-act threshold arrives before the must-act threshold, and the final duty is compulsory.
Recap
- Rule 16 puts the first early substantial action on the give-way vessel.
- Rule 17 progresses from keep course and speed, to may act, to must act.
- Continuous risk assessment is what lets the skipper recognise each stage in time.
Optional quick check
Section 7 of 9
When may a stand-on vessel first take avoiding action by her manoeuvre alone?
Continue studying COLREGs
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