Vessels In Sight Of One Another

The encounters

"In sight of one another" means literally that — both vessels can see each other visually. Once visibility drops, you switch to Rule 19 (see Restricted Visibility module). In sight, the rules below decide which of you alters and which holds course.

Rule 14 — Head-on

Two power-driven vessels meeting on reciprocal or nearly reciprocal courses, with risk of collision. Both alter starboard so each passes on the other's port side. Tell-tale: you see both sidelights of the other vessel (red and green), or her masthead lights in line. If in doubt that you're head-on — assume you are.

Rule 15 — Crossing

Two power-driven vessels crossing so as to involve risk of collision: the vessel which has the other on her own starboard side is the give-way vessel. She must alter and shall, if circumstances admit, avoid crossing ahead of the other. The vessel that sees the other on her port side is the stand-on vessel.

Rule 13 — Overtaking

An overtaking vessel is one approaching another from a direction more than 22.5° abaft her beam — in plain terms, you can see her sternlight at night without seeing either sidelight. The overtaking vessel always gives way and must keep clear until finally past and clear. If in doubt that you're overtaking, assume you are. Once an overtaking encounter, always an overtaking encounter — even if the bearing later shifts to a crossing aspect.

Rule 12 — Sailing vessels

When two sailing vessels approach so as to involve risk of collision: (i) the vessel with the wind on her port side shall keep out of the way; (ii) when both have the wind on the same side, the windward vessel keeps out of the way; (iii) if you cannot determine the wind side of the other, give way.

Rule 17 — Action by stand-on vessel

The stand-on vessel maintains course and speed — predictably, observably. She may take action when it becomes clear that the give-way vessel is not taking appropriate action; she must take action when collision cannot be avoided by the give-way vessel's action alone. When forced to act in a port-crossing case, she shall not alter to port for a vessel on her own port side.

The simulator's role

Reading the rules and recognising a real encounter at sea are two different skills. The simulator builds the second. Each scenario presents a target on AIS, on radar, and through the bridge windows — you must classify it (head-on, crossing, overtaking) within the first 30 seconds, identify your duty (give way or stand on), and act accordingly.

The free demo scenario "Head-on" walks you through a textbook Rule 14 case in clear visibility. The full course adds night versions where you must classify by side-lights and stern-light alone, plus multi-target scenarios where you simultaneously stand-on for one vessel and give-way for another.

Common mistakes

• Confusing crossing with overtaking — if the target is more than 22.5° abaft your beam, it's overtaking even if the geometry feels like a crossing.
• Stand-on vessel altering course early — Rule 17 requires you to maintain course and speed. Premature action can confuse the give-way vessel and cause the very collision you're trying to avoid.
• Altering to port in a head-on — both vessels must turn starboard. A port turn invites a starboard-altering opponent into your path.
• Treating "sailing-vs-power" as automatic priority — true on open water in sight, but Rule 18 may shift priority and Rule 9/10 override entirely (see related modules).
• Crossing ahead of the stand-on vessel — Rule 15 explicitly says don't.