Head-on Situation.
(a) When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter her course to starboard so that each shall pass on the port side of the other.
(b) Such a situation shall be deemed to exist when a vessel sees the other ahead or nearly ahead, and by night she could see the masthead lights of the other in a line or nearly in a line and or both sidelights, and by day she observes the corresponding aspect of the other vessel.
(c) When a vessel is in any doubt as to whether such a situation exists, she shall assume that it does exist and act accordingly.
This should be not so much a rule as an instinct: when approaching another vessel anywhere near head-on, always turn to starboard.
Remembering Rule 8, this course change must be made without delay and must be positive enough, that the other vessel can see and recognise your actions. Subtle corrections will not be noticed and could cause confusion.
An important factor to note, is the wording of paragraph (b). This emphasises paragraph (a) and indicates that this rule applies not only when you are exactly head on to each other, but also when you are nearly head on. Experience will dictate when a head on situation no longer exists but has become a crossing situation (or vice versa). A good rule of thumb however, would be that a head on situation exists if you have a relative aspect of within approximately 5 degrees of the other vessel. This would be when the masthead lights are nearly in line and only one of the sidelights would be visible.
All the above, should be regarded as being “head on” situations because the masthead lights are very nearly in line and by day, the situation would appear to be “head-on”. Additionally, there is an element of doubt so the watchkeeper would obey Paragraph C and assume that the situation exists and act accordingly.
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