Lateral marks indicate the port and starboard sides of a channel or fairway in the conventional direction of buoyage.
Region A (used through Europe, Africa, most of Asia and Australia):
- Port-hand mark: red, usually can or cylindrical, red light if lit
- Starboard-hand mark: green, usually conical, green light if lit
Region B (used in the Americas, Japan, the Republic of Korea and the Philippines):
- Port-hand mark: green, usually can or cylindrical, green light if lit
- Starboard-hand mark: red, usually conical or nun, red light if lit
The essential point is the direction of buoyage. In many approaches it is from seaward toward harbour, but rivers, estuaries and local systems may define it differently on the chart.
At a channel division, a modified lateral mark identifies the preferred channel: it retains the lateral main colour and topmark, with one broad horizontal band of the opposite colour. Its light is composite group flashing Fl(2+1), in the main colour. In the conventional direction, keep the can-shaped mark to port for a preferred channel to starboard; the arrangement reverses for a preferred channel to port.
An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
Buoyage Reading Order
Read the mark in a fixed order: topmark, colour pattern, light rhythm, charted meaning, then the safe side or action required.
Confirm the conventional direction of buoyage from the chart or pilotage plan before deciding port-hand or starboard-hand treatment.
Treat every mark as one aid among several.
Cross-check with charted depth, position, radar, visual bearings and the planned track.
Exam Focus
For cardinals, use the cones first, then the colour bands, then the flash mnemonic.
If those three agree, the answer is usually secure.
For lateral marks, the region only changes the colours, not the core idea: the mark still identifies the side of the channel in the conventional direction of buoyage.
Key Takeaways
Region A means red to port when returning from seaward; Region B means red to starboard
The region changes the colours but not the idea that the marks identify the channel sides
Can-type marks identify one side and conical-type marks identify the other
Always confirm the conventional direction of buoyage on the chart or pilotage information
Common Mistakes
Memorizing colours without first checking the direction of buoyage
Assuming every river or harbour approach uses the same seaward reference without chart confirmation
Test Your Knowledge
Practise this topic and review the explanation for each answer.
More rules in this Part
- IALA Isolated Danger MarksAn isolated danger mark is on or near a danger with navigable water around it. Consult charts and nautical publications for the extent of the danger and safe passing distance.
- IALA Safe Water MarksIndicate navigable water all around. Red and white vertical stripes with a single red sphere topmark.
- IALA Special MarksYellow marks indicating special areas such as ODAS, traffic separation, military exercise areas, or cables/pipelines.
- IALA Emergency Wreck Marking BuoyMarks new dangers, including wrecks. 1 s blue + 0.5 s darkness + 1 s yellow + 0.5 s darkness; period 3 s.
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