Collision Avoidance in Fog on the Scheldt
You are the skipper of a 15-metre motor yacht on the Scheldt near Antwerp. The fog has suddenly thickened, reducing visibility to about 50 metres. You are proceeding at 12 knots (about 22 km/h) on a course of 270° (west). Your radar is on and shows a large echo about 0.5 nautical miles ahead, slightly to starboard, moving slowly. You hear a fog signal of one prolonged blast followed by two short blasts from that direction. The tide is flooding, setting you to the east at about 1 knot. There is a traffic separation scheme nearby, and you are not sure of your exact position. You have a crew of three, all on deck wearing life jackets. You need to decide how to avoid collision.
1. What does the fog signal indicate about the other vessel, and what are your obligations under CEVNI?
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The fog signal of one prolonged blast followed by two short blasts is the signal for a vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel constrained by her draught, a sailing vessel, a vessel engaged in fishing, or a vessel engaged in towing or pushing. Given the context of a large echo moving slowly, it is likely a large vessel such as a ship or a tug with tow. Under CEVNI, in fog, you must proceed at a safe speed and have proper regard for the visibility. You must also sound the appropriate fog signals: for a power-driven vessel making way through the water, one prolonged blast at intervals of not more than 2 minutes. Since you hear the other vessel's signal, you must determine if risk of collision exists. If so, you must take action in ample time. The other vessel may be the stand-on vessel if you are crossing, but in fog, both vessels must take action to avoid collision. You should reduce speed immediately to the minimum at which you can maintain steerage, and be prepared to stop.
2. What manoeuvre should you take to avoid collision, considering the radar information and the tide?
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The radar shows the other vessel about 0.5 nautical miles ahead, slightly to starboard, moving slowly. With visibility of 50 metres, you have very little time to react. You should immediately reduce speed to bare steerage way. Then, alter course to port to pass astern of the other vessel, as altering to starboard would take you across her bow. However, you must ensure that altering to port does not put you into the path of other vessels or into shallow water. The flooding tide setting you east means that if you stop, you will drift eastwards, which could set you towards the other vessel if she is to the east. Therefore, you should maintain steerage way and make a substantial alteration to port, and sound the appropriate manoeuvring signal (one short blast) to indicate your alteration. If the other vessel is indeed a large ship, she may not be able to manoeuvre quickly, so you should take early and decisive action. Keep monitoring the radar and listen for further fog signals.
3. What additional precautions should you take given the proximity to a traffic separation scheme and the limited visibility?
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In a traffic separation scheme, you must follow the rules of the scheme, which typically require you to proceed in the general direction of traffic flow in the appropriate lane. However, in fog with limited visibility, you should consider whether it is safe to continue. If you are unsure of your position, you should reduce speed further or stop and anchor if safe to do so, but anchoring in a traffic lane is prohibited. You should try to determine your position using GPS, radar, and depth soundings. If you can, contact the port authority on VHF to inform them of your situation and ask for assistance. You should also post extra lookouts, use radar and AIS if available, and make fog signals. Ensure all crew are aware of the situation and are prepared for emergency procedures. If the fog is too thick, consider diverting to a safe anchorage outside the traffic scheme.