IALA Buoyage System – Best Easy-to-Understand Guide

by | Last updated Nov 24, 2023 | Navigation, Shipboard Operations | 0 comments

Like traffic lights, road signs, markings, retro-reflectors, and early warning devices, seafarers also use similar arrangements in waterways aimed at the safety of navigation.

We call them the IALA Buoyage Systems or the International Association of Marine Aids to Navigation and Lighthouse Authorities.

The IALA Buoyage Systems are sets of rules dedicated to buoys, lighthouses, light floats, and various watermarks. 

Included in that system are their shapes, colors, top marks, lights, and light characteristics to organize the safe movements of vessels.

These buoys can either be fixed objects or anchored at or near the points of interest.


The earliest known method for establishing a uniform system of buoyage dates back to 1889.

Certain countries agreed that the port side channel be marked with black color can buoys while the starboard channel with red conical buoys.

However, it didn’t go well when they introduced lights into the buoys. The Americans started placing red lights on red buoys while Europeans placed red lights on the black port hand buoys.

There were many attempts to re-establish such standards. One of them was in 1936 when they introduced the Cardinal and Lateral Systems under the League of Nations.

But as with many other attempts, many countries did not conform and continued their own buoyage systems for the reason that they were not assignation to that assembly.

Comparison of Lateral Marks color differences placed on the channels of Region A and B.
International Association of Marine Aids to Navigation and Lighthouse Authorities

What is IALA

IALA is a non-profit organization focusing on the safe and efficient movements of vessels through standardized Aids to Navigation.

Established in 1957, IALA is the only technical organization for marine aids to navigation. It has hundreds of members worldwide with all of them aiming to harmonize maritime buoyage systems.

There is a common misconception among seafarers as they tend to interpret IALA as the buoyage system.

A map of the world showing which countries are using the The IALA Buoyage Systems A and B.
The IALA Buoyage System.

For clarification, IALA creates the buoyage system used in sea lanes all over the world. 

They standardize the positioning, size, types, color, top marks, lights, and signals of buoys that aid ships in their passage in and out of ports.

Currently, IALA divides the world into two regions of buoyage namely Region A and Region B.

Types of Marks

IALA identifies six different marks as part of the buoyage systems to promote safe navigation.

They have specific shapes, sizes, colors, top marks, retro-reflective properties, light characteristics, numbers, and sound properties.

Since some of these aids are fixed, they can also be used for position fixing when conducting marine navigation near the coast.

Here are the following.

1. Lateral Marks

Lateral marks indicate the port and starboard side of the channel in a direction with the conventional flow of the voyage. It’s easy to spot them because they use red and green colors.

In this system, there are two regions one must be aware of before entering any ports or harbors. 

You must identify which area or country your ship is sailing in to determine if you will use Region A or Region B.

This is usually the job of the Second Mate but as part of the bridge team, you must also verify if what he’s written is true.

Region A

Region A sets red buoys on the port side and green buoys on the starboard side of the vessel when she is inbound at a port or terminal.

When outbound, the ship’s starboard side will now have red buoys while her port side will have green buoys.

Countries using Region A Buoyage Systems are the following:

  • Africa
  • Australia
  • Europe
  • India
  • New Zealand
  • The Gulfs, and
  • Most of Asia.
Lateral marks for IALA Buoyage Region A showing their shapes color, light flashes, and the direction of the buoyage.
IALA Buoyage Region A.

Region B

Region B is the opposite of the latter. 

When a ship is entering a port or channeling from the sea to her berth, she must set red buoys on her starboard side and green buoys on her port side.

Countries using Region B Buoyage Systems are the following:

  • North America
  • Central America
  • South America
  • North and South Korea
  • Japan, and
  • The Philippines.

In both regions, one must be aware of preferred channel marks which can be found when a channel bifurcates in two directions.

Lateral marks for IALA Buoyage Region B showing their shapes color, light flashes, and the direction of the buoyage.
IALA Buoyage Region B.

2. Cardinal Marks

Cardinal marks indicate the best navigable water against a particular danger or point of interest close to the mark itself.

We call them as such because they make use of the points or quadrants of a compass to indicate the safe side to pass.

Cardinal marks use yellow and red colors and double cone marks arranged in certain manners.

To use these marks, you are safe if you pass North of a North Cardinal Buoy, South of a South Cardinal Buoy, East of an East Cardinal Buoy, and West of a West Cardinal Buoy.

The Cardinal Marks North, South, East and West showing location relative to the Point of Interest.
Cardinal Marks.

The top marks for North and South Cardinal Buoys are very easy to identify. However, the East and West marks can be quite confusing. 

To help you out, I use these techniques to recognize them separately. I got it from my Chief Officer when I was still a deck cadet.

For West Cardinal Mark, W stands for WINE GLASS. I’m associating it with its top mark. 

For its body color, upon reciting them as yellow-black-yellow, I immediately associate them with West since (the last color) yellow ends in W!

After mastering that, the East Cardinal buoy is just easy to spot.

Tips for recognizing the West Cardinal Mark using its top mark as Wine Glass and color as yellow-black-yellowWest.

Light Signals

During nighttime, you can tell their light signals by comparing them to a clock, the North mark being 12 O’clock and so on.

The North mark has continuous flashing lights, the East mark has three, the West mark with 9, and the South has six flashes plus a long flash at the end.

3. Isolated Danger Marks

An isolated danger mark indicates a hidden danger to ships like shoals, wrecks, submerged rocks, or any obstruction that has navigable water around it.

These dangers may be well offshore or close to the shore but separated by a narrow channel like shoals.

In both regions using IALA, an isolated danger mark has a black color with a red band in the middle. It also has two big black balls displayed vertically.

Isolated Danger Marks of IALA Regions A & B having the colors black with red bands and two black balls on its top marks.
Isolated Danger Marks of IALA Regions A & B.

4. Safe Water Marks

We usually find this mark installed as a landfall buoy, mid-channel mark, centerline mark, or to point to the best area of passage in a fixed bridge.

A safe water mark indicates navigable waters all around the mark.

It has a red and white vertical stripe, either shaped as a spar or pillar with a single red sphere as a top mark.

A Safe Water Mark with red and white stripes, retroreflector on its top, and its light characteristics..
A Safe Water Mark.

5. Special Marks

Special marks indicate an area in the sea with specific purposes, the nature of which is displayed on the relevant charts.

These features include military exercise zones, recreation zones, ODAS buoys, spoil grounds, and many others.

Special marks are yellow-colored buoys with an “X” top mark (also yellow) and a yellow flashing light.

Navigators encountering such marks must check the relevant charts as to the details of their placements.

Special Marks of IALA A and B with different shapes but having the same yellow color throughout its body and an "X" top mark.
Special Marks of IALA A and B.

6. Emergency Wreck Marking Buoy

Emergency wreck marking buoys initially indicate newly discovered dangers which are not yet shown on nautical documents.

This buoy is clear, unambiguous, and highly conspicuous. We can find them positioned as close to the hazard as possible. It is deployed within the first 72 hours of the wreckage.

One of its features is blue and yellow stripes with an upright yellow cross top mark. On top of that, it has an alternating blue and yellow light.

The creation of this type of mark occurred later than the previous five. It happened when a collision between two ships left one of them underwater in 2002.

A ship passing close by an Emergency Wreck Marking Buoy with yellow and blue stripes and a marking that says "WRECK".
Emergency Wreck Marking Buoy.

Soon after, a vessel passing by hit the sunken wreck which was already marked. Then again, another ship struck the same wreck which happened in the Strait of Dover.

Authorities normally remove emergency wreck marking buoys when they make a proper marking of the obstacle. 

Additionally, relevant organizations published the wreck in nautical documents with the establishment of a full survey of the danger.

Buoyage Uniformity

The IALA Buoyage Systems have played a pivotal role in standardizing the use of buoys, lighthouses, and other navigational aids worldwide. 

It was established with the primary goal of enhancing the safety and efficiency of maritime navigation

These systems, categorized into Region A and Region B, have brought much-needed uniformity to the shapes, colors, and markings of these vital maritime aids.

May the winds be in your favor



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