As power-driven vessels drive on the right, and turn to the right if they meet head on, they also give way on their right hand side when they meet in a crossing situation.
At night, if you see a red light you must give way, a green light means you are the stand on vessel.
There is a saying which some people find useful:If to starboard, should red appear, it's your duty to keep clear!
This rule only applies to power-driven vessels, not sailing vessels (see Rule 12.)
The vessel giving way could do so by turning to starboard to pass astern, to port to run parallel which has the advantage of reducing the closing speed, slowing down, stopping or turning 180 degrees and running away! In some situations it may be sufficient to increase your vessel's speed.
The choice depends on what is a safe and seamanlike approach in the prevailing conditions.
Whichever action is chosen should be one that makes your intentions clear to the other vessel as quickly as possible. At night that will probably be one that changes the aspect of your vessel to display a different coloured light, something that immediately communicates to the other vessel what you have done.
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