COLREG / ARPA / AIS Bridge Rule 25(a) Rule 25(c) 🔒 Course / Premium

Rule 25 — Sailing Vessel Underway Lights

NIGHT. You see an approaching vessel showing: red & green sidelights; white sternlight (she is heading generally toward you and slightly past); NO...

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Scenario briefing

NIGHT. You see an approaching vessel showing: red & green sidelights; white sternlight (she is heading generally toward you and slightly past); NO masthead light at all. Optionally: two all-round lights at the top of the mast RED OVER GREEN. What type of vessel is this?

Applicable COLREG rule(s)

Rule 25(a) — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

Rule 25(c) — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

📸 Night recognition — 8 aspects

The same vessel rendered every 45° of aspect — bow, starboard bow, beam, quarter, stern, port quarter, beam, bow. Use this strip to learn how the lights present from each approach angle. Click any image to view full size.

Sailing vessel under way viewed head-on (bow aspect) — COLREG Rule 25 night-recognition diagram — Bow

Sailing vessel under way viewed from her starboard bow — COLREG Rule 25 night-recognition diagram — STBD bow

Sailing vessel under way viewed from her starboard beam — COLREG Rule 25 night-recognition diagram — STBD beam

Sailing vessel under way viewed from her starboard quarter — COLREG Rule 25 night-recognition diagram — STBD qtr

Sailing vessel under way viewed dead astern (stern aspect) — COLREG Rule 25 night-recognition diagram — Stern

Sailing vessel under way viewed from her port quarter — COLREG Rule 25 night-recognition diagram — Port qtr

Sailing vessel under way viewed from her port beam — COLREG Rule 25 night-recognition diagram — Port beam

Sailing vessel under way viewed from her port bow — COLREG Rule 25 night-recognition diagram — Port bow

Why it matters

COLREG knowledge is the foundation of safe ship handling. Most maritime collisions happen because watchkeepers either misidentified the situation, applied the wrong rule, or acted too late. This scenario lets you train pattern recognition + correct response under time pressure — the exact skill the rules are designed to support. RYA, Yachtmaster, STCW and most national exams expect you to apply COLREGs reflexively, not just recite them.

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