Here is more info as related to RESTRICTED VISIBILITY.

If you captaining a POWER vessel in an area of restricted visibility, then you must always have your engine ready for immediate maneuver.

The steering and sailing rules for vessels in restricted visibility apply to vessels navigating in or near an area of restricted visibility.

Here is another example of when you need to take action as soon as possible. You’re in a fog and you observe with radar that there is a risk of collision with a vessel 2 miles off your port bow. That action is to immediately take avoiding procedures.

Another example would be during restricted visibility that you detect by radar alone the presence of another vessel in a close quarter situation and a risk of collision exist. You should avoid altering your course toward a vessel abaft the beam.

Finally you here the fog signal of another vessel that is ahead of you. If there is a risk of collision you must stop your engines and navigate with caution.

As you have noted in the past post and this one it is extremely important to know what action to take during the time of restricted visibility.

Hugh Simpson