Every vessel coming up with another vessel from any direction more than 2 points abaft her beam—that is, in such a position with reference to the vessel which she is overtaking that at night she would be unable to see either of that vessel's side lights—shall be deemed to be an overtaking vessel, and no subsequent alteration of the bearing between the two vessels shall make the overtaking vessel a crossing vessel within the meaning of these rules or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear.
As by day the overtaking vessel can not always know with certainty whether she is forward of or abaft this direction from the other vessel, she should if in doubt assume that she is an overtaking vessel and keep out of the way.
ART. 25. In narrow channels every steam vessel shall, when it is safe and practicable, keep to that side of the fairway or mid-channel which lies on the starboard side of such vessel.
ART. 26. Sailing vessels under way shall keep out of the way of sailing vessels or boats fishing with nets or lines or trawls. This rule shall not give to any vessel or boat engaged in fishing the right of obstructing a fairway used by vessels other than fishing vessels or boats.
ART. 27. In obeying and construing these rules due regard shall be had to all dangers of navigation and collision and to any special circumstances which may render a departure from the above rules necessary in order to avoid immediate danger.
SOUND SIGNALS FOR VESSELS IN SIGHT OF ONE ANOTHER.
ART. 28. The words "short blast" used in this article shall mean a blast of about one second's duration.
When vessels are in sight of one another, a steam vessel under way in taking any course authorized or required by these rules shall indicate that course by the following signals on her whistle or siren, namely:
One short blast to mean, "I am directing my course to starboard."
Two short blasts to mean, "I am directing my course to port."