Traffic separation scheme marking

Broad arrows and a bounded zone dividing shipping lanes.

Also known as: TSS marking, Shipping lane marking, Separation zone

Maps & navigationSafety & hazardStandard profile

Meanings

A traffic separation scheme divides opposing streams of shipping with a separation zone between them, drawn as broad directional arrows either side of a bounded strip. Schemes adopted by the IMO carry legal force under the collision regulations, so the marking is a rule rather than advice.

Officially standardisedVerified fact
Divides opposing streams of shipping into one-way lanes separated by a zone, drawn with broad arrows showing the permitted direction.
Contexts: Navigation, Maps
Officially standardisedVerified fact
Carries legal force where the scheme has been adopted by the International Maritime Organization, being enforceable under the international collision regulations.
Contexts: Navigation, Maps

Visual description

Two broad open arrows pointing in opposite directions with a bounded strip of tinted area drawn between them.

Symmetry: none
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Topographic map
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional description of a mark, its usual name and where it is encountered. Where an issuing body defines the mark, that body is cited alongside and governs.
Ordnance Survey map symbols and legends
Ordnance Survey · retrieved 2026-08-01
The national mapping agency's own published legend. Authoritative for British Ordnance Survey mapping and for nothing else — the same drawing may carry a different meaning on another country's maps, and every record citing this states its jurisdiction.
U.S. Chart No. 1 — Symbols, Abbreviations and Terms used on Paper and Electronic Navigational Charts
National Oceanic and Atmospheric Administration · retrieved 2026-08-23
The published key to United States nautical charts, open and complete. Cited for chart symbology; the equivalent British publication is Admiralty 5011 and the two agree in most respects because both follow IHO specifications.
Admiralty Chart 5011 — Symbols and Abbreviations used on Admiralty Charts
United Kingdom Hydrographic Office · retrieved 2026-08-23
The British chart key. Cited for Admiralty chart conventions; not read in full, and records claim only the published symbol meanings.
Nautical chart
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol depicts and which authority publishes it, not for the legend of any particular chart series or the text of any standard.

Last reviewed 2026-08-23

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Topographic map and nautical chart symbols

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Meanings

Officially standardisedVerified fact

Divides opposing streams of shipping into one-way lanes separated by a zone, drawn with broad arrows showing the permitted direction.

Contexts: Navigation, Maps

Officially standardisedVerified fact

Carries legal force where the scheme has been adopted by the International Maritime Organization, being enforceable under the international collision regulations.

Contexts: Navigation, Maps

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Topographic map
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional description of a mark, its usual name and where it is encountered. Where an issuing body defines the mark, that body is cited alongside and governs.
Ordnance Survey map symbols and legends
Ordnance Survey · retrieved 2026-08-01
The national mapping agency's own published legend. Authoritative for British Ordnance Survey mapping and for nothing else — the same drawing may carry a different meaning on another country's maps, and every record citing this states its jurisdiction.
U.S. Chart No. 1 — Symbols, Abbreviations and Terms used on Paper and Electronic Navigational Charts
National Oceanic and Atmospheric Administration · retrieved 2026-08-23
The published key to United States nautical charts, open and complete. Cited for chart symbology; the equivalent British publication is Admiralty 5011 and the two agree in most respects because both follow IHO specifications.
Admiralty Chart 5011 — Symbols and Abbreviations used on Admiralty Charts
United Kingdom Hydrographic Office · retrieved 2026-08-23
The British chart key. Cited for Admiralty chart conventions; not read in full, and records claim only the published symbol meanings.
Nautical chart
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol depicts and which authority publishes it, not for the legend of any particular chart series or the text of any standard.

Last reviewed 2026-08-23