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Work out your safe speed, reaction time in fog
Divide the visibility by your speed and that is your reaction time before you reach an obstacle
that has only just come into sight.
Calculator
With five hundred metres of visibility and eight knots you have a good two minutes. That sounds like a lot, but it is not: spotting, assessing, deciding and manoeuvring all take time, and the other vessel may be making way too. This is why the collision regulations require a safe speed, one that allows you to stop within the distance you can see.
A collision in fog at a speed not suited to the conditions is the classic case in which the question of gross negligence is raised. Radar and AIS do not relieve you of that duty; they are no substitute for a proper lookout.
Some policies waive the defence of gross negligence up to a share of the sum insured; the limit varies by tariff. It is a safeguard, not a free pass.
Frequently asked questions
What speed is appropriate in fog?
One that allows you to stop within half the distance you can see.
Will the insurer pay after a collision in fog?
In some policies yes, through a waiver of the defence of gross negligence up to a share of the sum
insured.
Worked out for your type of boat
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