The Perils in Traffic Separation Schemes (TSSs)

31st March 2016

The Perils in Traffic Separation Schemes (TSSs)

Initial Report

Over 400 commercial vessels pass through the Dover Strait daily; the statistics for Malacca (where 4825 Very Large Crude Carriers (VLCCs) alone transited in 2013) are similar. Other choke points are all getting busier. By definition TSSs are established where traffic density is high and navigation constrained. These are therefore places where the dangers of navigation are amplified. At CHIRP we are reminded by a considerable ‘postbag’ in the last quarter of this fact ……

What did the reporters tell us?

OVERTAKING IN A TSS. A VLCC heading north-east in the Sandettie TSS was overtaken at very close quarters (1–2 cables) by a container ship. This manoeuvre necessitated her passing F1 buoy, marking the separation line at a distance of about 50 metres. The manoeuvre took place at the entrance to the NE lane, where the VLCC and to an extent the overtaking vessel were heavily constrained by their draught. The container ship did not comply with guidance on the relevant chart and in BA5550 advising against use of the Deep Water Route (DWR) by
vessels under 16 metres in draught, and to the dangers of overtaking. Extracts from the information reported to CHIRP. The reporter commented: ‘I was contacted by large container vessel bound for Hamburg making 21 kts (ship name) astern of me on channel VHF 16 & 6 stating he would ‘squeeze’ past me at entrance to DW route. I responded that I was a deep draught vessel and could not deviate from my course. On approaching Sandettie SW buoy with F1 buoy right ahead, container vessel contacted me again on VHF 16 to request I alter my course to starboard to give him a little more room, I stated that with his draught (13m) he should not be using DW route and should pass south and east of Sandettie especially as two deep draught vessels were now using the DW route and also that he should not be overtaking in the DW route. I started my alteration into the DW route early to give a little more sea room as he passed very close on my portside. [Ship] was also extremely close to crossing into the SW bound lane when passing the deep draught bulk carrier ahead of me … Many NE bound vessels with draught less than 16m use the DW route against recommendations, and are not questioned/advised by Griz Nez Traffic or Dover CG. This may be OK when no deep draught vessels are in or approaching the route, but to continue this practice (and overtaking) when the route is in use is asking for trouble’. The overtaking ship offered a different perception of some of the circumstances, but commented: ‘we certainly realize that the situation was more or less self-inflicted. It should never have taken place as good practice would have been overtaking the VLCC on her starboardm side, allowing own vessel to make the planned alteration of coursen towards starboard – or by slowing down until ample room available’.

 

tss

sandettie

dwr

The Lessons to be Learnt

It is the obligation of the overtaking vessel to “keep out of the way of the vessel being overtaken … until finally past and clear”. The distance at which the container ship, at speed, passed the VLCC (see photograph) was far too close. There was no spare room. Though we do not have tidal information (height or stream) which may have influenced decisions, it is clear that the VLCC judged he had little or no space to starboard. The OVERTAKING manoeuvre should not have taken place. Moreover, interaction will almost certainly have been present; this can cause loss of heading control or – at the least – unpredictable rudder requirements to maintain course (dependent on ships’ sizes and speeds, and the depth of water in which they were navigating). Though not in itself a factor in the rights and wrongs of collision avoidance, it is a fact that a collision where this manoeuvre took place could have closed the strait to deep draught vessels bound NE, or at the very least obstructed the route, with major consequences. Why did this happen? Was it inexperience? Was it a failure to think ahead? Was it a lack of prior planning? Was it red-line-itis (the tendency once a passage plan has been ‘entered’ to follow it regardless)? Whatever the cause, the container ship’s managers did acknowledge that she could or should have slowed down.

CHIRP Suggests

Passage planning and thinking ahead. The passage plan should normally conform with local routeing and manoeuvring guidance (in this case applicable to use of the Deep Water Route), with alternatives available as appropriate. Plan the TSS arrival: how, when, with what bridge manning, including decisions on the Master’s presence.

Execution. Remember that a plan is a plan; a basis for change if real time circumstances demand. It is never a line to follow regardless, if ‘the circumstances of the case’ dictate something different. When approaching the entrance to a TSS – indeed whenever navigating in a TSS – OsOW (appropriately backed up with extra expertise to manage workload) should be planning how to ‘slot into’ the traffic flow from a distance; in the case of these two large ships from at least 10 nautical miles. Slow down if in doubt, always remembering the ship astern. Things can happen very fast. Inexperienced OsOW can be sucked into close quarters situations that never need to occur. Don’t overtake if there is not ample time to the CPA and space to do so, within the available safe straight part of a TSS; if at all possible the overtaking vessel should only pass on the starboard side of the vessel to be overtaken in order to permit flexible options and maximise searoom.

Masters, by order book or verbal instruction, can clarify their expectations and calling orders with respect to speed and course alterations, overtaking, traffic density and the like. Use your eyes. Look up and out. Use electronic aids, certainly; but do not depend on them alone. Think from the other ship’s point of view. Are you own actions obvious and clear? Or might they induce doubt?

Doubt = DANGER.

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