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In the Netherlands, we have two buoyage systems: the SIGNI system on inland waterways and the IALA-A system at sea. Let’s start with the SIGNI and end with the only difference in the IALA-A system.

In both systems we have lateral (buoyage at the edge of fairways) and cardinal buoyage (indicating a wreck, sandbank or other obstacle). Buoys float and beacons are set on the ground. There are buoys (with light), barrels (no light).

Marking and buoys always have the following characteristics:

  • Day mark = Shape (pointed, blunt, convex, pillar)
  • Lighting character and colour
  • (Sometimes) top sign
  • Colour (green, red, black, yellow, white)
  • Radar reflector
  • Marks: the abbreviation of the fairway Number
lateral buoyage

Light characters

The faster the light characters the more dangerous. The period is the cycle of light and dark phases. The different types of light characters are:

  • Q=Quick Flash=flicker light (VQ=Very Quick and UQ= Ultra Quick)
  • Fl=Flash=glare light (Lfl=Longflash)
  • ISO=Isophase=Isophase light (ISO 2s = 1 second on and 1 second off)
  • Oc=Occulting=Interrupted-light (group interruption = multiple interruptions in 1 period)
  • Mo=Morsecode=Morsecode F=Fixed=Fixed light
light characters


The direction is towards the sea in the SIGNI system (inland water) and towards land in the IALA-A system (at sea). We start at sea with a safe water buoy indicating the start of the channel. When we enter the harbour from sea, we have the green, pointed odd-numbered buoys to starboard and a red blunt even-numbered buoy to port. So we then sail in the direction of the IALA-A system. If we then sail into the estuary, we enter the SIGNI system and suddenly sail against the direction. So the direction is a theoretical term, which you will rarely have to use in practice, as it applies both at sea and on inland waterways. So you always sail into a port “red on red and green on green”. To starboard we have a green boarding light (and green buoys) and to port we have a red boarding light (and red buoys). Another mnemonic is “A sailor leaves the sea with his heart bleeding.” His heart is on the left and he colours the left buoys red.


Ports and junctions may be marked with or without lights. When entering, the port side will see a red white horizontal striped marking, possibly with a red light, and the starboard side a green white horizontal striped marking, possibly with a light.

Vlieland harbour

Additional marking

Additional marking indicates a kind of cycle path outside the main channel for pleasure boats.

Light lines and sector lights

Looking towards the harbour, we can tell if we are sailing in the middle of the channel by looking at the line of lights. These are 2 lighthouses, the front one being lower than the back one. If we see the 2 lights perpendicular to each other, we are in the middle of the channel on the light line.

light lines

When objects other than lights are used, we call it a guide line.

Sometimes the fairway is indicated by a sector light. This is a light that shines a different colour over the different sectors. For example, we can see from the chart that if we are in the channel, we see white light. If we are to the right of the channel we see a green light and if we are to the left of it we see a red light.

sector light

Cardinal marking

Cardinal marking is marking of obstacles on wide waterways. A north cardinal means safe fairway north and an obstacle south of the buoy. The top marks point to part on the buoy that is black. The lights are like the dial of a clock (3, 6 and 9). The LFL clearly distinguishes the south cardinal from the west cardinal.

north cardinal

Separation of navigable waters

In the SIGNI system, there are 3 separation buoys:
A round buoy, above green and below red with a pointed top sign.

signi green partingston

A round buoy, red above and green below, with a blunt top sign.

signi red partingston

A round buoy with horizontal red and green stripes, with a round top sign. For waterways of equal importance.

waterways of equal importance

Special marking

Special marking indicates a special area such as an anchorage area, practice area, fishing area, speedboat area, competition areas, etc. The colour is yellow and the top sign a horizontal cross.

Isolated danger

Isolated danger buoys are black with red band. The top sign consists of 2 black spheres. The light is a white group flashing light. The mark is the abbreviation or name of the obstacle (e.g. name wreck, BANK).

Safe waters

Marked safe fairways are in the middle of the safe fairway. You can therefore pass them left and right at an appropriate distance (see the chart for that). They are round and red white vertically striped and have no top sign in the SIGNI to avoid confusion with the round separation buoys. As a light, they have a white ISO 8s or LFL. The mark is the abbreviation or name of the fairway.


At sea there is the IALA-A system and the separation of navigable waters / fairways is indicated in a different way by: Lateral separating bouys or cardinal separating buoys:

Example 1: Red lateral separation buoy

Separationston IALA-A

Example 2: Green lateral separation buoy

Partingston IALA-A green

Example 3: Cardinal separation with waterways of equal importance.

Separationston IALA-A equal

Questions & Answers

Question 1: You can see the rear higher light of a set of leading lights on the right and the lower light more to the left. You need to go to…

a: Starboard
b: Port
c: Stay on this course

Question 2: An isophase light is a light character whose light relative to the darkness is…

a: is shorter
b: is longer
c: the same

Question 3: Sailing in the English Channel between UK and France towards the Netherlands you have the following buoys on the starboard side:

a: Red blunted
b: green pointed
c: Green Blunted

Question 4: What marks a yellow barrel?

a: Separate hazard
b: waterway
c: Special area

Question 5: On which side should you pass a buoy that is black at the top and yellow at the bottom?

a: North
b: East
c: South

Question 6: One yellow-black-yellow buoy means that the safe waterway is located at:

a: East
b: West
c: South

Question 7: What does yellow blue vertical striped buoy mean?

a: a separate hazard
b: forbidden area
c: New uncharted obstacle

Question 8: A red and white vertically striped buoy is a:

a: Safe water mark
b: fairway buoy
c: Both are correct

Question 9: At night, what is the light character of a beacon that is yellow above and black below?

a: Q
b: Q(6) + LFL 15s
c: Q(9) + LFL 15s

Question 10: In the IALA-A system, you sail against the buoy direction. You will see a pointed, green buoy with a red band. To keep the side waterway you have to keep the buoy on…?

a: It’s impossible to say
b: port side
c: starboard