Act early. Act large. There have been several collisions in crossing situations where the give way vessel waited too long to make the course alteration.
Mariners draw their own inferences from the terms “ample time”, or “substantial” where the measure could be very inconsistent from one individual to the other. The question for every officer of the watch should be to consider the possibility and practicability of altering course well in advance to avoid a collision or a close quarter situation. An alteration of course made at, say, 5 nm range is a lot safer than a substantially large alteration made at 1 nm. This gives the stand on vessel a clear signal of the intention of the give way vessel and avoids ambiguity.
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Insight Collisions – why do they occur?
Case study Collision with fishing vessel