Overtaking before Árpád Bridge with oncoming traffic
You are master of a 65 m motor tanker, light, proceeding downstream on the Danube in Budapest at about 14 km/h over the ground. Current is 2.3 m/s. Ahead, a 110 m pushed convoy is making 6 km/h over the ground in the same direction, slightly left of mid-channel. Árpád Bridge is 800 m ahead; its navigable span is 100 m wide. An oncoming 90 m passenger vessel is 1.5 km beyond the bridge, showing normal lights. Your Inland AIS shows the convoy's speed and course but no VHF acknowledgment. To overtake before the bridge you would need about 12 minutes in the narrow approach; passing through the span side-by-side is not possible. The convoy's stern is 250 m ahead. Wind is light; visibility is good. Your schedule allows a 30-minute delay. Your vessel draws 2.1 m; the convoy draws 2.8 m; the span has a marked shoal on the right bank.
1. What is the controlling constraint on overtaking, and what do you do in the next 5 minutes?
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The controlling constraint is the bridge span, not the convoy's speed. The convoy is 800 m from the span at 6 km/h, so it will reach the approach in roughly 8 minutes. My vessel at 14 km/h covers 800 m in about 3.4 minutes, and the closing speed is about 8 km/h. A 12-minute overtake cannot be completed before the narrow span, and side-by-side passage through a 100 m span with a marked shoal is not acceptable. Attempting to force the overtake would create a three-vessel meeting at the bridge and leave no abort space. In the next five minutes I would reduce speed to match the convoy, keep a safe following distance of at least 250–300 m, call the convoy and the passenger vessel on VHF with names and positions, and state that I will follow the convoy through the span. I would not rely on the oncoming vessel to clear the span for me. I would keep the engine ready for immediate manoeuvre and monitor Inland AIS.
2. The passenger vessel calls on VHF and asks you to pass the convoy before the bridge so it can clear the span. How do you reply, and what sound signal do you use?
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I would refuse the request. The passenger vessel may prefer me to pass before the bridge, but I cannot create a safe passing lane before the span, and an overtake started now would either be incomplete at the bridge or force a side-by-side entry. I would reply on VHF that I am following the convoy through the span and that the passenger vessel should maintain a safe course on its side, or wait if necessary. In CEVNI narrow-channel practice, the upstream vessel must be prepared to give way, but that does not give me a right to force an unsafe overtake. If I alter course to starboard to line up for the span, one short blast is the appropriate manoeuvring signal; if I need to reduce speed or go astern, three short blasts. The VHF agreement should be explicit: who goes first, on which side of the span, and what happens if the convoy slows.
3. After the bridge, the convoy slows and signals you to pass. What checks before starting the overtake?
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Before overtaking I would check: a clear span and sufficient water for both vessels; no oncoming traffic visible on AIS, radar, or visually; the convoy's explicit agreement on VHF; which side I will pass; the position of the marked shoal; and the effect of bank suction and squat. I would also confirm my own draught and the convoy's 2.8 m draught against the available depth. I would start the overtake only on a straight reach with room to abort, keep a lateral separation of at least one beam, pass at a moderate speed to limit suction and wash, and not cut across the convoy's bow. I would sound the appropriate manoeuvring signal and keep a listening watch. If the convoy speeds up, the span closes, or an oncoming vessel appears, I would abandon the overtake and fall back astern.