COLREG / ARPA / AIS Bridge Rule 23(d) 🔒 Course / Premium

Rule 23(d) — PDV < 7 m AND < 7 kn

NIGHT. A very small power-driven vessel is observed. Her length is less than 7 m and her maximum speed does not exceed 7 kn.

🔒

This scenario is part of the full library. Unlock all 54 COLREG scenarios with the Skipper Refresher Course (€99.99, lifetime + certificate) or a Premium subscription (from €29.99/mo).

Buy Skipper Refresher — €99.99 Or get Premium — from €29.99/mo

Scenario briefing

NIGHT. A very small power-driven vessel is observed. Her length is less than 7 m and her maximum speed does not exceed 7 kn. She exhibits ONE all-round WHITE light and, if practicable, sidelights. No masthead light, no separate sternlight. What allowance permits this reduced lighting?

Applicable COLREG rule(s)

Rule 23(d) — 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.

Power-driven vessel under 7 m and under 7 kn viewed head-on (bow aspect) — COLREG Rule 23(d) night-recognition diagram — Bow

Power-driven vessel under 7 m and under 7 kn viewed from her starboard bow — COLREG Rule 23(d) night-recognition diagram — STBD bow

Power-driven vessel under 7 m and under 7 kn viewed from her starboard beam — COLREG Rule 23(d) night-recognition diagram — STBD beam

Power-driven vessel under 7 m and under 7 kn viewed from her starboard quarter — COLREG Rule 23(d) night-recognition diagram — STBD qtr

Power-driven vessel under 7 m and under 7 kn viewed dead astern (stern aspect) — COLREG Rule 23(d) night-recognition diagram — Stern

Power-driven vessel under 7 m and under 7 kn viewed from her port quarter — COLREG Rule 23(d) night-recognition diagram — Port qtr

Power-driven vessel under 7 m and under 7 kn viewed from her port beam — COLREG Rule 23(d) night-recognition diagram — Port beam

Power-driven vessel under 7 m and under 7 kn viewed from her port bow — COLREG Rule 23(d) 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.

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.