COLREG in easy language (Rule 19)

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Rule 19 Conduct of vessels in restricted visibility

(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 collision 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.


Restricted visibility includes fog, mist, snow, heavy rain and sandstorms but according to Rule 19 this means any situation where you cannot see the other ship or its navigation lights. Rule 19 applies also when the vessel is far enough and is detected “by radar alone”.

Different rules apply in restricted visibility: Rules 13, 14, 15 and 17 are no longer in force. Rule 19 has to be strictly applied. As a result you are no longer “stand-on” vessel for the vessels coming from your port side, there is no more overtaking or head-on rule, all actions needs to be taken as per Rule 19. All vessels are give-way vessels.

Every vessel must take action and every vessel must proceed at safe speed with its engines ready for immediate maneuver.

Rule 19 divide the horizon in two parts and give strict and simple collision avoidance rules for each slice:

a) Avoid altering course to port for a vessel for a vessel forward of the beam, except for a vessel you are overtaking.

b) Avoid altering course towards any ship abeam or abaft the beam. You must assess if your ship is getting close to another ship and/or if there is a risk of collision. Remember connected rules:

• Rule 7 on risk of collision – there is a risk of collision if you are in any doubt.

• Rule 5 on look-out – you must always maintain a proper look-out by sight and hearing.

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