(a) This Rule applies to vessels not in sightVessels shall be deemed to be in sight of one another only when one can be observed visually from the other. of one another when navigating in or near an area of restricted visibilityThe term 'restricted visibility' means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes. .
(b) Every vesselThe word 'vessel includes every description of water craft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water'. shall proceed at a safe speed adapted to the prevailing circumstances and conditionsThis phrase is used in Rules 5,6,7 & 19. It indicates to the reader that the rule must be considered within the context that it is being applied. Although this type of 'catch-all phrase' makes the rules challenging to interpret it allows mariners to respond to the variety of events that can occur at sea. More of restricted visibility. A power-driven vesselThe term 'power-driven vessel' means any vessel propelled by machinery. shall have engines ready for immediate manoeuvre.
(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.
(d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collisionThe term risk of collision is described in Rule 7. 'Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.' More exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:
(i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;
(ii) an alteration of course towards a vessel abeam or abaft the beam.
(e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.