A Crossing Situation – Collision Avoidance

30th June 2016

A Crossing Situation - Collision Avoidance

Initial Report

A container vessel reported failure of a give way passenger ship – on the reporter’s port bow with a closest point of approach (CPA) ‘close’ on the starboard bow – to alter course to starboard for him when requested. A VHF exchange showed that the passenger ship considered the CPA safe. The reporter (having maintained course and speed) remained concerned, made a 360 degree turn to starboard, and continued on his track, passing under the stern of the other vessel.

What did the reporter tell us?

The reporter considered that the passenger ship’s crossing ahead distance (around 2 nautical miles (nm)) and CPA (around 1 nautical mile) were too small; this is shown on the automatic radar plotting aid (ARPA) screen shot below. It depicts true vectors in this case. VHF communications were promptly established. The exchange may be summarised as follows: reporter – “What are your intentions”; passenger ship: “I will maintain my course and speed”; “CPA less than 1nm … you are in breach of COLREG 15; advise you pass astern”; “negative … CPA more than 1nm; there is no risk of collision”.

What did the passenger ship’s company tell us?

Company orders in the past have dictated a minimum CPA of 2 nautical miles ‘when reasonable and practical’. This stipulation has changed; the decision is now left to individual Masters. In this case the Master considered the situation safe, and stood on. Others might have acted differently.

The lessons to be learnt

Were the crossing and CPA distances acceptable? It is proper that judgement ultimately lies with ships’ Masters given all the circumstances. That said, a minimum 2 nm CPA in open water is widely accepted as good practice. In this case, with a crossing range ahead of 2 nm, the CPA on the starboard bow of the stand-on vessel was bound to be around 1 nautical mile. The stand-on vessel had every right to express concern; in this event, it was incumbent on the other to act accordingly and to give way, even if she considered the stand-on CPA safe. This action would also have been consistent with traditional good manners and respect between seafarers. A crucial principle is to think from the point of view of the other ship, especially if she is larger or more burdened. If she is concerned, doubt exists; doubt = danger. Mariners should also always consider how the position might look in the event of a machinery or steering gear breakdown, and stopping distances in such a case. From 1 nautical mile, very close quarters situations can develop very quickly. Were the actions of the stand-on (reporter’s) vessel correct? The reporter considered a risk of collision to exist; he was well within his rights to do so. COLREG 7 is quite clear: “If there is any doubt such risk [of collision] will be deemed to exist”. In principle he could have slowed down, or he could have turned to port once the other vessel was across his bow (at which point a crossing situation would have no longer existed). What he could not have made is a turn to port before that time. In this circumstance a 360° turn to starboard is reasonable as an action of last resort. However caution is essential. Below a certain range, the manoeuvre can become dangerous. It must also take full account of all other vessels in the vicinity, including those astern and on either side, especially in constrained waters such as TSSs; situational awareness and orientation (in other words an alert all-round lookout) are therefore vital in such circumstances. Notwithstanding these cautions, no criticism of the reporter is implied in this case; when the circumstances are suitable, a 360° turn can be safe, as in this instance; valuable time can be bought.

CHIRP Suggests

“If there is doubt, a risk of collision exists”. Thus it is incumbent on a ‘give-way’ vessel’ (and also a matter of good manners) in a crossing situation to alter if the stand-on vessel expresses concern. Doubt is always accompanied by danger and risk of miscalculation. Avoid use of VHF if possible; it can be a distraction from the correct actions when time is tight. Think from the point of view of the other ship; what may seem safe and reasonable to one may not from the other’s bridge. Maintain the habit of constant ‘what-ifing’: “what if my steering gear failed now”?

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