Stand-On — Last-Moment Action (Rule 17(b)(c))
Crossing situation target on your PORT quarter/beam is the give-way vessel but is NOT altering.
Scenario briefing
Crossing situation target on your PORT quarter/beam is the give-way vessel but is NOT altering. Rule 17(a)(ii): as stand-on you may take action when it becomes apparent the other is not acting. Rule 17(b): when collision cannot be avoided by give-way alone, take best action. Rule 17(c): if you do alter, do NOT turn to PORT for a vessel on your own port side.
Applicable COLREG rule(s)
📸 Bridge simulator scene
Captured directly from the SkipperCheck COLREG bridge simulator at scenario T = 0 — the moment the encounter begins.
Key teaching points
- Rule 17(a)(ii): MAY take action when it becomes apparent the give-way vessel is not acting in compliance.
- Rule 17(b): SHALL take such action as will best aid to avoid collision when by the give-way vessel's action alone collision cannot be avoided.
- Rule 17(c): when the stand-on is a power-driven vessel altering for another on her own port side, she shall NOT alter to port.
- A speed reduction is often safer than a turn at the very last moment — Rule 17 does not require a turn.
Common mistakes to avoid
- Turning to port toward the give-way vessel "to pass behind her". Rule 17(c) explicitly forbids this geometry.
- Acting under 17(a)(ii) too early and effectively becoming the give-way vessel — gauge "apparent" carefully.
Why it matters
Exam relevance
Rule 17(a)(ii)/(b)/(c) transitions are a frequent advanced-level COLREG probe in Yachtmaster Offshore and STCW OOW orals.
Related scenarios
About SkipperCheck simulators
SkipperCheck offers two browser-based maritime training simulators:
- ARPA · AIS · COLREG Bridge Simulator — 54 scenarios covering Rules 2, 5–10, 12–19, 23–30, 34 and 35.
- VHF SRC Radio Simulator — 15 scenarios: voice Mayday, DSC distress, Mayday Relay, Pan-Pan, Sécurité, routine.
Both run in any modern browser, on desktop or mobile. No install, no plugins.