(a). Notwithstanding anything contained in the Rules of part B, sections I and II, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.
Rule 13: OVERTAKING
Rule 13 has no exceptions; the overtaking vessel always keeps out of the way. If you are not sure whether you are overtaking another vessel, then Rule 13 says that you are. Once you are an overtaking vessel, you’ll remain an overtaking vessel until the other vessel will be clear. Remember:
a) Always presume the other ship does not know you are there.
b) If possible avoid crossing ahead – it is always safer to cross astern.
c) Do not pass close – overtaking always takes time, so make sure both ships have plenty of room to maneuver. Never assume that the other ship will maintain its course and speed.
d) Even the rule allows you to choose the side, if possible try to overtake the other vessel in her starboard side, in this way you will keep your starboard side clear for future maneuvers (most of the COLREGs are involving an alteration of course to starboard).
e) Beware of interaction – if you are forced to pass close, be very careful of interaction between the two vessels.