Restricted visibility Rule19

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:

(ll) An alteration of course towards a vessel abeam or abaft the beam.	(l)An alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;