COLREG / ARPA / AIS Bridge Rule 19(d) Rule 8 ✓ Free demo

RV — Target Right Ahead (Rule 19(d))

Fog. Visibility under 0.5 NM. A target has been detected by radar right ahead, closing on reciprocal course. Take action in ample time.

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Scenario briefing

Fog. Visibility under 0.5 NM. A target has been detected by radar right ahead, closing on reciprocal course. Take action in ample time. Rule 19(d)(i) prohibits an alteration of course to PORT for a vessel forward of the beam (except when overtaking). Achieve a CPA of at least 1 NM, then click EVALUATE.

Applicable COLREG rule(s)

Rule 19(d) — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

Rule 8 — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

📸 Bridge simulator scene

Captured directly from the SkipperCheck COLREG bridge simulator at scenario T = 0 — the moment the encounter begins.

SkipperCheck bridge simulator — COLREG Rule 19(d) — Restricted visibility — target right ahead — radar PPI with AIS targets — Bridge-simulator scene under COLREG Rule 19(d) — Restricted visibility — target right ahead. Captured from the SkipperCheck COLREG / ARPA / AIS bridge simulator.

Key teaching points

Rule 19(d)(i): if a target is forward of the beam (other than overtaking), DO NOT alter course to PORT.
Rule 19(b): proceed at safe speed adapted to restricted visibility.
A substantial starboard alteration (≥30°) opens CPA quickly and is readable on the other vessel's radar.
Combine with a speed reduction if room is tight (Rule 19(e)).

Common mistakes to avoid

Altering to port "because she'll do the same" — Rule 19 has no head-on convention; do not assume the other vessel's action.
Making a 10° starboard alteration. In fog at 0.5 NM visibility, that is not enough to give CPA in the time available.

Why it matters

A target detected by radar dead ahead in fog is the classic Rule 19 problem — there is no stand-on or give-way, every vessel acts on her own, and the geometry forbids a port alteration. Watchkeepers who try to "split the difference" with a small port turn create the wrong manoeuvre.

Exam relevance

Rule 19(d)(i) port-prohibition is a fog-scenario classic in RYA Yachtmaster Coastal/Offshore and STCW OOW orals.

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