Night Collision Risk in the Traffic Separation Scheme off Cape Town
You are the skipper of a 14 m motor yacht on a night passage south of Cape Town, crossing a traffic separation scheme at about 02:00. Visibility is good, about 6 nm, with a moderate SW swell. You are making 8 knots on a course of 180° true. On your starboard bow you see a steady white masthead light and, below it and slightly to the right, a red sidelight. On your port bow, further away, you see a green sidelight and a white masthead light. A third vessel is overtaking you from astern, showing a white sternlight and a masthead light. The crossing vessel on your starboard bow is closing steadily. You have AIS but the crossing vessel is not transmitting.
1. Identify each of the three vessels as far as the lights allow, and state your obligations under the collision regulations for each.
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Vessel on starboard bow (masthead + red sidelight): You are seeing her port side and her forward masthead light, so she is a power-driven vessel crossing your bow from starboard to port, or meeting you. Because you see her red sidelight and a masthead light, she is likely crossing from your starboard side. Under the rules, a power-driven vessel crossing from your starboard side is the stand-on vessel; you are the give-way vessel. You must take early and substantial action to keep out of her way - normally by altering course to starboard and/or reducing speed, and you must avoid crossing ahead of her.
Vessel on port bow (green sidelight + masthead): She is showing her starboard side, so she is crossing from your port side toward your starboard. You are the stand-on vessel in that encounter; you must keep your course and speed, but you must still monitor and be ready to act if she does not give way.
Overtaking vessel astern (sternlight + masthead): She is overtaking you and must keep out of your way. You are the stand-on vessel; maintain course and speed and monitor her. If she does not alter, take action to avoid collision once it is clear she is not complying.
Priority: Deal with the give-way situation on your starboard bow first, because that is the closest and most immediate risk.
2. The crossing vessel on your starboard bow does not appear to be altering course. What actions would you take, in what order, and what would you avoid?
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Order of action:
- Early and substantial alteration: Alter course to starboard to pass astern of her, and/or reduce speed. A small alteration is not enough; make it obvious (a clear course change of at least 20–30° or a significant speed reduction).
- Sound signal: If necessary, sound one short blast to indicate 'I am altering my course to starboard', and if in doubt, at least five short and rapid blasts to signal doubt or danger.
- Monitor: Keep watching her lights and bearing. If the bearing remains constant and the range closes, the risk of collision is real and you must take further action.
- Last resort: If collision cannot be avoided by the give-way vessel's action alone, the stand-on vessel may also take action - but she should avoid, if possible, altering course to port for a vessel on her own port side, and should not turn across the bow of the other vessel.
Avoid:
- Do not alter course to port to pass ahead of a crossing vessel on your starboard side.
- Do not make a series of small alterations; make one clear, early, substantial alteration.
- Do not assume the other vessel has seen you simply because you can see her - she is not transmitting AIS, so treat her as potentially unaware.
- Do not turn broadside to the swell or into the path of the overtaking vessel while manoeuvring.