Three sets of lights
Night traffic by lights alone. Advanced level, about 4 min. COLREGs Rules 15, 18, 23–26.
The situation
A dark night with good visibility. You are under power, heading north. Three vessels are in sight, and all you can see of them are their lights: one fine on your starboard bow, one dead ahead, and one on your port bow.
What do you do?
- Alter boldly to starboard: Pass astern of A, port to port with B, away from C.
- Hold on: A and B have to sort themselves out: Keep your course and speed.
- Alter to port, away from Contact A: Open the distance from the crossing ship.
Lookout: Identify each vessel by her lights first, then work out the duties pair by pair. Use the binoculars, and board a contact to see what she sees.
Each vessel’s duty
Contact A: Stand on for you, keep clear of the yacht
Masthead light, red sidelight. What is Contact A? A white masthead light with a red sidelight is a power-driven vessel underway, seen from her port side: she is crossing from your right to your left.
You are on her port side, so towards you she is the stand-on vessel. Contact B is a sailing vessel, so towards her Contact A is power-driven and keeps out of the way.
Contact B: Stand on for you and Contact A
Red and green sidelights, no white light above them. What is Contact B? Red and green together mean you are dead ahead of her. With no masthead light above, she is a sailing vessel.
Rule 14 is for two power-driven vessels. A sailing vessel meeting you head-on is still a sailing vessel, and power-driven vessels keep out of her way under Rule 18.
Contact C: Keep her course and speed; the others keep clear
Green over white all-round lights, and a green sidelight. What is Contact C? Green over white all-round lights mark a vessel engaged in trawling. Her green sidelight shows you see her starboard side, so she is crossing from your left to your right.
A vessel engaged in fishing is kept clear of by power-driven and sailing vessels alike, so she is the stand-on vessel towards everyone here.
Your sound action
Alter boldly to starboard
You keep out of the way of all three: Contact A under Rule 15, the sailing vessel and the trawler under Rule 18. A bold starboard alteration passes astern of A, leaves the yacht to port, and opens the distance from the trawler.
Why the other options fall short
Hold on: A and B have to sort themselves out
Every one of the three is a vessel you must keep clear of. Holding on leaves the yacht ahead of you and Contact A crossing from your starboard side unresolved.
Alter to port, away from Contact A
Turning to port heads you towards the trawler and her gear, and across the bow of a vessel you must keep clear of. At night a port turn is also hard for the others to read.
Rules 15, 18, 23–26 · Lights and responsibilities
Lights tell you what a vessel is and which way she is heading. Duties follow from what she is: power-driven vessels keep out of the way of sailing and fishing vessels, and in a crossing between two power-driven vessels the one with the other on her starboard side gives way.