Crossing traffic in a buoyed approach channel - who gives way, and how much?
MV BIGHT HARVESTER, a 189 m bulk carrier making 12.4 kn, is outbound through a buoyed approach channel steering 000° T. The master is below after a long pilotage; you are the sole OOW with an AB at the wheel and a lookout forward. Visibility is 5 nm, wind SW force 3, sea slight.
At 0340 the X-band ARPA, on relative vectors, shows two targets that matter. Target A bears 040° R at 6.0 nm; her range has fallen about 1.4 nm every six minutes with no change in the visual bearing. ARPA gives A course 270° T, speed 10 kn, CPA 0.1 nm, TCPA 22 minutes. Target B is a laden tanker overtaking on your port quarter, bearing 155° R at 1.4 nm, speed 14.5 kn, passing 0.3 nm to port. A 10 m shoal and the port-hand channel edge lie 0.9 nm to port. To starboard is a dredged berth area, clear of traffic, with soundings of 12 m or more.
The master's standing orders require a call for any predicted CPA under 1 nm, but also tell you not to call him for "routine crossings".
1. Who is the give-way vessel, and precisely what manoeuvre do you make? Give the rule basis, the heading you would steer, and why that size of alteration.
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Risk of collision. A's bearing is steady while the range falls 1.4 nm every 6 minutes. That is the classic Rule 7(d) test, so risk of collision exists and I must not wait for the CPA to prove it. I confirm the ARPA picture with a visual bearing and a radar plot rather than trusting a single source.
Who gives way. A is steering 270° T, so from A my bearing is 220° T - about 50° on A's port bow. A therefore has me on her port side; I have A on my starboard side. Under Rule 15 the vessel with the other on her starboard side keeps clear, so A is stand-on and I am the give-way vessel. The fact that A is on my starboard bow confirms, and does not replace, that geometry check.
Manoeuvre. I alter course to starboard in one movement, at least 60°, to steer 060° T, and do it now at 6 nm rather than at 2 nm.
Reasoning.
- Rule 16 requires early and substantial action; Rule 8(a) requires it in ample time with a positive result.
- Rule 8(b) requires the alteration to be large enough to be readily apparent to the other vessel on radar. A 60° change at 6 nm opens the CPA to roughly 3 nm and puts me astern of A's track, satisfying the Rule 15 instruction to avoid crossing ahead.
- Rule 8(d) warns against a succession of small alterations - 10° at a time leaves A unable to read my intentions.
- Rule 8(e): with sea room and a clear dredged area to starboard, a bold course change is the most effective option; no reduction of speed is needed.
Why not to port. A port alteration would turn me towards the shoal and channel edge 0.9 nm to port, and would close B overtaking on my port quarter. B must keep clear under Rule 13, but I must not make a manoeuvre that forces her into an avoidance action.
2. Do you call the master, and what do you put in the bridge records? Include the sound signal and your view on using VHF or AIS to talk to A.
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Calling the master. The master's standing order is a call for any CPA under 1 nm, and the predicted CPA was 0.1 nm, so the call is required. Crucially, the call does not delay the manoeuvre - Rule 8 requires action in ample time, and an OOW who waits for the master before acting has already lost the plot. I make the alteration, then call the master immediately with a one-line situation report: target A, bearing, range, my alteration, new course, and Target B overtaking to port.
Sound signal. In sight of A and altering course to starboard, Rule 34(a) requires one short blast. I make it as the helm goes over, not afterwards.
Records. The bridge notebook and the logbook should show: time of first detection and the bearing/range; the ARPA course, speed, CPA and TCPA; the visual bearing confirming the steady bearing; the time the helm was applied, the heading at which the swing started/paused, and the time the new course 060° T was steadied on; the sound signal; a fresh bearing and range after steadying; the time the master was called and the time he arrived on the bridge; and A's continued track. B's data goes in as well, since she constrains the manoeuvre. The bell book shows the telegraph movements if any.
VHF and AIS. I do not use VHF to negotiate the crossing. Radio agreements between ships create their own ambiguity, are not recognised by the COLREGs, and have contributed to many collisions. If A calls, I keep it to a factual statement of my manoeuvre and log it. AIS is an identification and information tool, not a collision-avoidance sensor - displayed data can be stale and the CPA/TCPA derived from a poorly entered draught or heading is not to be relied on over radar and visual bearings.
3. Six minutes later A has still not altered and B has increased speed and now sits 0.8 nm on your port quarter. What changes?
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Does A's inaction matter? A is the stand-on vessel and is entitled to hold her course and speed. She is not obliged to act, so her silence is not evidence that I have misread the situation. What matters is whether my alteration produced a safe CPA. I take a fresh visual bearing and range and check the ARPA's new solution. If the bearing is now opening and the CPA is around 3 nm, the situation is resolved and Rule 8(d) tells me not to keep fiddling with small successive changes. If the CPA is still unsatisfactory, I make a further substantial alteration - another 20–30° to starboard - or reduce speed, leaving no doubt about my intentions.
B closing from the port quarter. B is the overtaking vessel and must keep clear under Rule 13, and she must continue to do so until finally past and clear. My duty is not to embarrass her: I hold my new course and speed and avoid any further port alteration that would cut across her. Having turned to starboard, the distance between us is opening rather than closing, which is the desired outcome.
Escalation. If B continues to close, I sound the appropriate signal, call her by name on VHF channel 16 or 13, and inform the master, who by now is on the bridge. I do not assume B has seen me because AIS shows her watchkeeping details.
Record. I note the times of the bearing checks, B's increasing speed, the sound signals and any VHF exchange. A COUREG case turns on what was seen and done at what minute, and the notebook is the evidence.