Observe and identify
Advanced level, about 3 min. International COLREGs / IRPCS.
The situation
At night in good visibility, a contact approaches from your port side on a closing bearing. You are under power at six knots. Inspect the lights and assess your duty while she remains in sight. A fog bank will reach the area shortly; changing visibility will require a fresh assessment.
What is your initial duty in the visible encounter?
- Power-driven crossing from port: initially keep course and speed
- A sailing vessel: assume you must turn for sail
- Power-driven crossing from port: ignore her until she is past
Answers and explanations
Lookout: Establish the vessel configuration from the visible lights, then apply the crossing relationship. Keep checking that the other vessel acts and that visual contact remains available.
When the situation changes
Fog has arrived and visibility is now 60 m. The contact is no longer in sight. The supplied stopping assessment establishes that six knots is unsafe in these conditions, while two knots permits effective avoiding action and stopping within an appropriate distance. Your engines can be kept ready for immediate manoeuvre.
Reduce to the supplied two-knot safe speed and reassess
Rules 6 and 19(b) require a safe speed adapted to restricted visibility and engines ready for immediate manoeuvre. The checkpoint supplies this vessel’s stopping assessment. The earlier stand-on duty does not justify retaining a speed now established as unsafe.
Keep six knots because you initially stood on
An earlier stand-on duty does not override safe-speed requirements when visibility changes. Six knots has now been established as unsafe for the supplied stopping ability.
Turn to port at six knots from her last seen position
The last visible track does not establish the contact’s present movement. Keep a proper lookout, adapt speed to the new visibility and reassess.
The sound answer
Power-driven crossing from port: initially keep course and speed
The masthead and green sidelight fit a power-driven vessel seen from her starboard side. With this vessel crossing from your port side, you initially stand on under Rules 15 and 17. She takes avoiding action in this authored replay. Keep monitoring; this initial duty does not establish the response to a later out-of-sight encounter.
Why the other options fall short
A sailing vessel: assume you must turn for sail
The elevated white masthead with a green sidelight is the authored power-driven configuration, rather than the ordinary sailing profile. Determine the duty from the complete configuration and encounter.
Power-driven crossing from port: ignore her until she is past
Standing on carries an ongoing lookout and reassessment duty. You must watch the other vessel’s action and changing conditions; maintaining course and speed does not justify ignoring her.
Rules 5, 6, 11, 15, 17 & 19(b) · Reassess as visibility changes
In an in-sight crossing between power-driven vessels, the vessel with the other on her starboard side keeps out of the way. The other initially keeps course and speed while checking the avoiding action. When fog arrives, adapt to a safe speed for the new conditions, keep engines ready and reassess the encounter.