Section II: Conduct of vessels in sight of one another
Meeting head-on: Rule 14
In practice
- Head-on: BOTH vessels alter course to starboard and pass port to port.
- At night you know the situation by the masthead light or lights in a line, or nearly in a line, ahead, with both sidelights in view at once.
- Doubt means you act as if the situation exists (paragraph c).
Top-down view, a schematic sketch. Red = gives way, green = stands on (keeps her course and speed).
Text of Rule 14: Head-on Situation
(a) When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision each shall alter her course to starboard so that each shall pass on the port side of the other.
(b) Such a situation shall be deemed to exist when a vessel sees the other ahead or nearly ahead and by night she could see the masthead lights of the other in a line or nearly in a line and/or both sidelights and by day she observes the corresponding aspect of the other vessel.
(c) When a vessel is in any doubt as to whether such a situation exists she shall assume that it does exist and act accordingly.
Text of the International Regulations as amended, quoted from the consolidated U.S. Coast Guard Navigation Rules (public domain); spelling follows the IMO original. When in doubt, the Convention decides.
The common mistake
Reading a "nearly head-on" meeting as crossing and waiting for the other ship to move. A classic trap: in doubt, Rule 14c orders you to assume head-on, so both go to starboard.
At night you know her by the lights
Set the bearing to 0 in the trainer. You see both sidelights and the masthead light. On a ship showing two masthead lights the after one sits higher than the forward one (a vessel under 50 m may show only one).