Restricted Visibility: Evidence, Rule 19 and Command

In or near restricted visibility, safe speed and a proper lookout are the starting conditions, not optional responses after a target appears. Have engines ready for immediate manoeuvre, display navigation lights, make the prescribed sound signals, and use radar systematically if fitted and operational. A target detected by radar alone is not treated as an ordinary in-sight crossing simply because AIS supplies a name and course.

Rule 19 requires avoiding action in ample time when a close-quarters situation is developing. So far as possible, avoid altering to port for a vessel forward of the beam other than one being overtaken, and avoid altering towards a vessel abeam or abaft the beam. These are not mechanical commands to turn starboard in every geometry; the radar plot, other targets, depth, traffic scheme, and sea room still determine the safe action.

If a fog signal is heard apparently forward of the beam and risk of collision has not been ruled out, or close quarters with a vessel forward of the beam cannot be avoided, reduce to the minimum speed at which the vessel can be kept on course. Take all way off if necessary and navigate with extreme caution until the danger is over. The inability to identify the signal accurately is a reason for more caution, not for assuming it belongs to a harmless target.

Brief measurable limits before entry: maximum speed, radar range scales, plot interval, minimum CPA policy appropriate to the circumstances, depth and cross-track limits, helm mode, sound-signal responsibility, and an escape or holding option. If radar, heading, depth, or position becomes unreliable, the plan must lose ambition before it loses safety margin.