Observe and identify
Advanced level, about 3 min. International COLREGs / IRPCS.
The situation
At this next authored checkpoint it is still night and visibility remains 60 m. You have reduced to two knots, your vessel’s minimum course-keeping speed. The contact is no longer in sight. A fog signal is apparently forward of your beam and collision risk has not been determined absent. Her last visible track does not establish her present movement.
Which assessment and action are supported now?
- Apply restricted-visibility conduct and keep minimum course-keeping speed
- Regain six knots because you were the stand-on vessel
- Turn to port based on her last visible track
Answers and explanations
Lookout: Check the current evidence and applicable conditions. An earlier in-sight duty and an old observed track do not settle the present out-of-sight encounter.
When the situation changes
No further signal is sounding at this instant, but the source remains out of sight. You have not established that collision danger is over. Silence between periodic fog signals supplies no new evidence of a clear passage.
Continue at minimum course-keeping speed with extreme caution
Continue with extreme caution until collision danger is over. Fog signals are periodic, so a quiet interval does not prove that the vessel or danger has gone. Taking all way off remains necessary if the developing circumstances require it.
Regain six knots because the signal stopped
Fog signals can be separated by intervals of up to two minutes. Silence at this instant does not establish that collision danger has ended.
Assume she has passed and stop monitoring
The vessel remains unseen and the current risk assessment is unresolved. The old crossing picture and a quiet interval do not discharge the continuing lookout and caution duties.
The sound answer
Apply restricted-visibility conduct and keep minimum course-keeping speed
These vessels are no longer in sight. The forward fog signal and unresolved collision risk require minimum course-keeping speed under Rule 19(e), with extreme caution. You are already at the supplied two-knot minimum; an earlier stand-on assessment does not justify regaining six knots.
Why the other options fall short
Regain six knots because you were the stand-on vessel
The present encounter must be assessed from its present conditions. Rules 11–18 concern vessels in sight of one another; this unseen encounter in restricted visibility is governed by Rule 19.
Turn to port based on her last visible track
The last observed track is not enough to establish the unseen vessel’s present movement. The apparently forward signal with unresolved risk calls for minimum course-keeping speed and continued assessment.
Rules 11, 19(e) & 35(a) · A new assessment after sight is lost
The in-sight steering rules require vessels to be visually observable. In restricted visibility with the source unseen, a fog signal apparently forward of the beam and unresolved collision risk call for minimum course-keeping speed, all way off if necessary, and extreme caution until danger is over. A power-driven making-way fog signal is periodic, not continuous.