Buoyage and Lateral Marks: Understanding IALA A and B

Buoys and beacons are the road signs of the sea. They mark the safe channels, warn of dangers, and show you which way to go. The system that gives them meaning is maintained by IALA, the international body for marine aids to navigation, and understanding it lets you read a coastline or an estuary at a glance. For European boaters this is doubly important, because Europe uses the IALA Region A system, which is the mirror image of the Region B system used in the Americas and parts of Asia.

This guide focuses on lateral marks, the buoys that define the sides of a channel, and explains the crucial “direction of buoyage” concept that makes the whole system work. It also touches on how Region A differs from Region B, a classic exam question, and how to keep the colours straight in your head.

What Lateral Marks Do

Lateral marks show the edges of a navigable channel. They come in two families, port-hand marks and starboard-hand marks, and by keeping them on the correct side of your boat you stay in safe water. In IALA Region A, which covers Europe, the colours are as follows.

• Port-hand marks are red. They are often can-shaped (flat-topped) and, if lit, show a red light. Keep them on your port (left) side when travelling in the direction of buoyage.
• Starboard-hand marks are green. They are often conical (pointed-topped) and, if lit, show a green light. Keep them on your starboard (right) side when travelling in the direction of buoyage.

A memory aid many European sailors use is that when returning to harbour, red marks are kept to port, sometimes remembered loosely as red aligning with the left as you come home. The catch, of course, is that this only works if you know which way the “direction of buoyage” runs.

The Direction of Buoyage

Lateral marks only make sense once you know the conventional direction of buoyage, because a port mark is only “port” when you travel that way. The rule is that the direction of buoyage generally runs from seaward toward the harbour, river or estuary, in other words the direction you take when returning from the sea. So as a general principle, when you are heading in from the open sea, you keep red port marks on your left and green starboard marks on your right. When you leave harbour and head out to sea, you are going against the direction of buoyage, so the marks are effectively reversed relative to your boat.

Around coasts, where there is no obvious harbour to head for, the direction of buoyage is defined by convention, often running in a set direction along the coastline, and it is printed on charts. The key exam point is that “port” and “starboard” marks are defined by the direction of buoyage, not simply by which is on your left or right at any given moment.

Region A Versus Region B

Here is where many candidates get caught out, so it is worth being precise. The world is divided into two IALA regions with opposite lateral colour conventions.

• In Region A, which includes all of Europe, Africa, most of Asia and Australia, port marks are red and starboard marks are green.
• In Region B, which covers the Americas, Japan, Korea and the Philippines, the colours are swapped: port marks are green and starboard marks are red.

A useful phrase for Region B is “red right returning,” meaning keep red marks on your right when returning from sea. In Region A, the European system, it is essentially the opposite. For a European exam you will almost always be working in Region A, but examiners sometimes ask about the difference to check that you understand the marks are colour-swapped, not fundamentally different in logic. The shapes, red cans and green cones, are the same in both regions; only the colours flip.

Beyond Lateral Marks

While this guide focuses on lateral buoyage, it helps to know that the IALA system includes several other mark types you will meet on the water and on the exam.

• Cardinal marks use black and yellow patterns and top-mark cones to tell you to pass to the north, south, east or west of a danger.
• Isolated danger marks are black with red bands and mark a specific hazard with navigable water all around.
• Safe water marks are red and white vertical stripes, often marking a channel centre or landfall.
• Special marks are yellow and indicate features such as anchorages, cables or restricted areas rather than the channel edges.

These other marks follow their own colour and shape logic, but lateral marks are the foundation and the most frequently tested, so make sure they are rock solid first.

Locking It In for the Exam

Buoyage questions reward clear, confident recall of colours, shapes and the direction of buoyage. Because Europe uses Region A consistently, most of your practice will centre on red-to-port and green-to-starboard when heading in from the sea, plus recognising when you are going the other way. In the boatingexamine course you can practise lateral and other buoyage questions in exam format, including the Region A versus Region B distinction, so the colours never trip you up on the day.

FAQ

In Europe, which colour mark do I keep to port? In Europe (IALA Region A), you keep red port-hand marks on your port (left) side when travelling in the direction of buoyage, which generally means when heading in from the sea toward a harbour or up a river. Green starboard marks go on your right.

What is the difference between IALA Region A and Region B? The lateral mark colours are reversed. In Region A (Europe and much of the world) port marks are red and starboard marks are green. In Region B (the Americas, Japan and others) port marks are green and starboard marks are red. The shapes stay the same; only the colours swap.

How do I know the direction of buoyage? The direction of buoyage generally runs from seaward into a harbour, estuary or river. Along open coasts it follows a conventional direction shown on the chart. Because lateral marks are defined relative to this direction, always establish which way it runs before deciding which side to leave a mark.