Part I: Foundations

Chapter 1: The Simple Idea

The sea has no roads

On land, traffic works because the road does most of the work for us. A road controls where vehicles can go. It points them in known directions. It keeps opposing streams apart. It funnels conflict into a few built places, like intersections and roundabouts, where signs and signals sort it out. The road rules for cars are only a thin layer on top of a physical system that does the hard part.

The sea has none of this. A vessel can go anywhere there is enough water. She can head in any direction, at any speed. Nothing like a kerb or a lane marking holds her in place. But sea traffic is not spread evenly across the ocean. It gathers in the same places, because every voyage is shaped by the same geography. Ships going between the same ports follow the same efficient tracks. They converge on the same straits, capes and channel entrances. They bunch up at the same harbour approaches. The result is thick streams of shipping that cross, meet and overtake each other in confined water, with nothing physical to keep them apart.

For most of maritime history this gap was filled by local custom and the judgement of each master. As ships became faster, larger and more numerous, that arrangement caused collisions at a rate that became intolerable. The answer was to do for the sea what the road does for the land, but to do it with words alone. One set of rules, the same everywhere, carried by every vessel wherever she goes. Those words are the COLREGs.

What the Rules are for

The International Regulations for Preventing Collisions at Sea exist to do one thing. They make every vessel’s behaviour predictable to every other vessel. Everything else about them follows from that one purpose: the way the instrument is built, the legal style of its language, even the parts that seem to contradict each other. This guide keeps coming back to this point. When a rule seems strange, the first question is not “what am I missing?” It is “what does predictability need here?” The answer is usually the rule.

It is worth building this up slowly, because the rest of the guide stands on it.

The problem the Rules solve

Think about what a collision situation really is. Two vessels are approaching each other. Each one is conned by a watchkeeper the other has never met. Their training, language, fatigue and skill are all unknown to the other side. There is often no reliable way to coordinate in the time available. A VHF call may go unanswered. It may reach the wrong ship. It may produce an agreement that one side then misunderstands. So each bridge has to decide what to do based almost only on what it can see of the other. And each one knows the other is doing the same.

This is not mainly a problem of skill. Two excellent mariners, each acting sensibly on their own, can still collide. This is because “sensible” allows more than one answer. Picture a head-on approach. Both vessels decide to turn away. One turns to port and the other turns to starboard. Each has acted reasonably, and together they have caused the collision they were both trying to avoid. What kills people in this situation is not incompetence but uncoordinated competence.

The solution is the same one used on every road in the world. It is a script. The keep-left rule does not work because driving on the left is better than driving on the right. It works because everyone follows it. That means every driver can predict what an oncoming driver will do, without knowing anything else about them. The COLREGs are that script for the sea. They tell both vessels in an encounter which role each one holds, and what that role must do. So two strangers who cannot talk to each other can still act together.

TRANSLATION

Rule 14(a) (MISCPUB 0127): “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.”

Plain reading: head-on, both turn right.

What the legal wording adds: it binds both vessels, not just one. It sets the trigger, which is risk of collision, not just being close. And it names the result to aim for, which is passing port side to port side. So neither watchkeeper has to guess whether the other thinks the rule applies, or what outcome they are steering for. The plain version tells you what to do. The rule tells you what the other vessel will do.

Predictability beats cleverness

Here is the most important result, and the one that takes longest to accept. A standard manoeuvre done predictably is safer than a better manoeuvre done in a way the other vessel does not expect. A watchkeeper might see a neat solution to a developing situation. It might be a small early adjustment that would fix everything, if only the other vessel understood it. The other vessel will not understand it. They will see a target that no longer matches the script. From that moment they are guessing, and a bridge that is guessing is dangerous.

This is why the Rules do not just tell you what to do. They tell you how to do it in a way the other vessel can read. Action should be taken early. It should be substantial, not a series of small changes. And it should be easy for the other vessel to see, whether by eye or by radar. This is exactly what Rule 8(a) and (b) require (MISCPUB 0127). The manoeuvre itself is a signal. A bold turn to starboard, made in good time, tells the other bridge three things at once. I have seen you. I understand the situation the same way you do. I am following the script. A series of small adjustments tells them none of this, however well those adjustments might work in fact.

PRACTICAL NOTE: the cost of being clever

The collision cases in the standard commentary are full of vessels that left the expected action for reasons that made sense to them at the time. An early turn to port to gain sea room. A drop in speed instead of a turn. A manoeuvre held back to see what develops. (Cockcroft & Lameijer, 7th ed, collects many such judgments.) Time and again the choice made sense on the bridge that made it. The collision happened on the other bridge, where it made no sense at all. The Rules do not ask you to be brilliant. They ask you to be easy to read.

Why knowing the words is not knowing the Rules

Many candidates have passed Rules of the Road exams by learning the text by heart. The authors of the standard commentary saw where this leads. Cockcroft and Lameijer open their guide (7th ed) by noting that candidates “have sometimes been encouraged to commit the Rules to memory but this does not necessarily result in a clear understanding of the contents.”

Rote knowledge fails at sea for a clear reason. The Rules are a script, but the script has judgement built into it on purpose. They do not define how narrow a narrow channel is. They do not define how close a close-quarters situation is. They do not fix the moment when a stand-on vessel must give up her course and act. These gaps are not mistakes, as Chapter 9 will show. They are places where the drafters handed the decision to the mariner, because no fixed rule could cope with the huge variety of real encounters. A watchkeeper who has only memorised the text reaches exactly these points, which are the points where collisions actually happen, with nothing to apply. The text has handed the problem back, and rote learning gives no way to take it up.

So understanding the Rules means understanding three things the text alone will not give you. The first is why it is structured the way it is, so you can find the governing rule under pressure (Chapter 5). The second is why it is written in legal language, so you can read exactly what it requires and what it leaves open (Chapter 6). The third is what it expects of you in the gaps it leaves on purpose, which the Rules call the ordinary practice of seamen (Chapter 10).

Where this guide goes

Part I builds that understanding. It covers where the Rules came from, who they bind, and why a warship of the Royal Australian Navy holds itself to them. It covers how the instrument is put together, how to read its language, and what its words mean. And it covers how encounters develop and bring the Rules into play, why the apparent contradictions exist, and what good seamanship actually demands. Part II then works through every rule in number order. Because no rule works alone, each analysis also maps how that rule interacts with the Rules it changes, gives way to, or overrides. Part III puts the method to work in worked scenarios, both civilian and naval.

One sentence to carry through all of it. The Rules make you predictable, and predictability is what keeps ships safe.