You are here

The role of duty officers in collision avoidance

The role of duty officers in collision avoidance

Taking consideration of various court claims involving maritime casualties, Harry Hirst of Ince&Co. law firm discussed the importance of "the use of time" by duty officers (OOW) in collision avoidance.

Namely, in the latest edition of Signals Newsletter, Mr. Hirst notes distance is often a criteria that OOWs apply when taking action, however avoiding action should always be about timing and not about distance. Avoiding action is frequently taken too late, with OOWs waiting until the other vessel is about 2 or 3 miles away before altering course.

Consider, for example, two container ships both proceeding at 20 knots on broadly reciprocal courses. Their combined speed of approach is 40 knots; and at 40 knots, the OOW who waits until the two vessels are about 2 to 3 miles apart before altering course is leaving himself only 3 to 5 minutes to avoid collision.

Reported cases suggest that “ample time” insofar as the give-way vessel is concerned when the two vessels are in sight of one another, and for both vessels when navigating in restricted visibility, is at least 12 minutes before the two vessels would otherwise collide; that is, by latest C-12.

For the stand-on vessel in a crossing situation, the reported cases suggest that the obligation to take action under COLREG Rule 17(b) is unlikely to arise before C-5. The stand-on vessel may of course, take avoiding action earlier under Rule 17(a) (ii), and will often be required to do so as a matter of good seamanship. Prior to taking action under this Rule however, the OOW should first alert the give-way vessel by sounding the signal prescribed in Rule 34(d), and then allow the give-way vessel a reasonable time in which to respond. A reasonable time would be in the order of 3 minutes or so, which suggests the stand-on vessel should be taking action under Rule 17(a)(ii) some time between C-9 and C-5; and this is consistent with the reported cases.


There can be no hard and fast rules dictating when and how the OOW should take action to avoid collision, but the following suggested guidelines, reiterating just everything that deck cadet officers are taught during training, may help:

Action to avoid collisions should be positive, bold and early
Alterations of course should be at least 30o
Action to avoid collision should be made in ample time:

(a) when giving away, by latest C-12
(B) when standing on by latest between C-9 and C-5.

Find out more here