COLREGs Rule 10: Traffic separation schemes
Last reviewed: October 14, 2026
Rule 10 governs how vessels behave in and near traffic separation schemes. A vessel using a scheme must proceed in the appropriate lane in the general direction of traffic flow. The International rule adds exemptions in (k) and (l) that the Inland rule does not contain.
Applies toInternational: traffic separation schemes adopted by the Organization. Inland: traffic separation schemes.
What it says
A vessel using a traffic separation scheme must proceed in the appropriate traffic lane in the general direction of traffic flow for that lane.
COLREGs Rule 10(b)(i)“proceed in the appropriate traffic lane in the general direction of traffic flow for that lane;”
A vessel must, so far as practicable, avoid crossing traffic lanes. If it must cross, it must cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
COLREGs Rule 10(c)“A vessel shall, so far as practicable, avoid crossing traffic lanes but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.”
A vessel must not use an inshore traffic zone when she can safely use the appropriate traffic lane within the adjacent traffic separation scheme. Vessels of less than 20 meters in length, sailing vessels and vessels engaged in fishing may use the zone.
COLREGs Rule 10(d)(i)“A vessel shall not use an inshore traffic zone when she can safely use the appropriate traffic lane within the adjacent traffic separation scheme.”
A vessel other than a crossing vessel or a vessel joining or leaving a lane must not normally enter a separation zone or cross a separation line, except in an emergency to avoid immediate danger or to fish within a separation zone.
COLREGs Rule 10(e)“shall not normally enter a separation zone or cross a separation line except:”
A vessel navigating near the terminations of traffic separation schemes must do so with particular caution.
COLREGs Rule 10(f)“A vessel navigating in areas near the terminations of traffic separation schemes shall do so with particular caution.”
A vessel must so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.
COLREGs Rule 10(g)“A vessel shall so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.”
A vessel engaged in fishing must not impede the passage of any vessel following a traffic lane.
COLREGs Rule 10(i)“A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane.”
International: A vessel restricted in her ability to maneuver while maintaining safety of navigation in a scheme is exempt from this Rule to the extent necessary to carry out the operation.
COLREGs Rule 10(k)“is exempted from complying with this Rule to the extent necessary to carry out the operation.”
Common questions
Who may use an inshore traffic zone?
Vessels of less than 20 meters in length, sailing vessels and vessels engaged in fishing may use the inshore traffic zone. Any vessel may also use it when en route to or from a port or other place within the zone, or to avoid immediate danger.
“However, vessels of less than 20 meters in length, sailing vessels and vessels engaged in fishing may use the inshore traffic zone.”
Can I anchor in a traffic separation scheme?
A vessel must so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.
“A vessel shall so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.”
How must I cross a traffic lane?
A vessel must so far as practicable avoid crossing lanes. If obliged to cross, it must cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
“if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.”
Must a vessel not using a traffic separation scheme stay away from it?
Yes. A vessel not using a traffic separation scheme must avoid it by as wide a margin as is practicable.
“A vessel not using a traffic separation scheme shall avoid it by as wide a margin as is practicable.”
The text of COLREGs Rule 10
U.S. Coast Guard, Navigation Rules and Regulations Handbook
Rule 10: Traffic Separation Schemes
International (COLREGs)
(a) This Rule applies to traffic separation schemes adopted by the Organization and does not relieve any vessel of her obligation under any other rule.
(b) A vessel using a traffic separation scheme shall:
(i) proceed in the appropriate traffic lane in the general direction of traffic flow for that lane;
(ii) so far as practicable keep clear of a traffic separation line or separation zone;
(iii) normally join or leave a traffic lane at the termination of the lane, but when joining or leaving from either side shall do so at as small an angle to the general direction of traffic flow as practicable.
(c) A vessel shall, so far as practicable, avoid crossing traffic lanes but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
(d) (i) A vessel shall not use an inshore traffic zone when she can safely use the appropriate traffic lane within the adjacent traffic separation scheme. However, vessels of less than 20 meters in length, sailing vessels and vessels engaged in fishing may use the inshore traffic zone.
(ii) Notwithstanding subparagraph (d)(i), a vessel may use an inshore traffic zone when en route to or from a port, offshore installation or structure, pilot station or any other place situated within the inshore traffic zone, or to avoid immediate danger.
(e) A vessel other than a crossing vessel or a vessel joining or leaving a lane shall not normally enter a separation zone or cross a separation line except:
(i) in cases of emergency to avoid immediate danger;
(ii) to engage in fishing within a separation zone.
(f) A vessel navigating in areas near the terminations of traffic separation schemes shall do so with particular caution.
(g) A vessel shall so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.
(h) A vessel not using a traffic separation scheme shall avoid it by as wide a margin as is practicable.
(i) A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane.
(j) A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane.
(k) A vessel restricted in her ability to maneuver when engaged in an operation for the maintenance of safety of navigation in a traffic separation scheme is exempted from complying with this Rule to the extent necessary to carry out the operation.
(l) A vessel restricted in her ability to maneuver when engaged in an operation for the laying, servicing or picking up of a submarine cable, within a traffic separation scheme, is exempted from complying with this Rule to the extent necessary to carry out the operation. One Another
Inland Rules
Traffic separation schemes
(a) This Rule applies to traffic separation schemes and does not relieve any vessel of her obligation under any other Rule in subchapter E ‡.
(b) A vessel using a traffic separation scheme shall:
(i) Proceed in the appropriate traffic lane in the general direction of traffic flow for that lane;
(ii) So far as practicable keep clear of a traffic separation line or separation zone;
(iii) Normally join or leave a traffic lane at the termination of the lane, but when joining or leaving from either side shall do so at as small an angle to the general direction of traffic flow as practicable.
(c) A vessel shall, so far as practicable, avoid crossing traffic lanes but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
(d) (i) A vessel shall not use an inshore traffic zone when she can safely use the appropriate traffic lane within the adjacent traffic separation scheme. However, vessels of less than 20 meters in length, sailing vessels, and vessels engaged in fishing may use the inshore traffic zone.
(ii) Notwithstanding subparagraph (d)(i) of this Rule, a vessel may use an inshore traffic zone when en route to or from a port, offshore installation or structure, pilot station, or any other place situated within the inshore traffic zone, or to avoid immediate danger.
(e) A vessel other than a crossing vessel or a vessel joining or leaving a lane shall not normally enter a separation zone or cross a separation line except:
(i) In cases of emergency to avoid immediate danger;
(ii) To engage in fishing within a separation zone.
(f) A vessel navigating in areas near the terminations of traffic separation schemes shall do so with particular caution.
(g) A vessel shall so far as practicable avoid anchoring in a traffic separation scheme or in areas near its terminations.
(h) A vessel not using a traffic separation scheme shall avoid it by as wide a margin as is practicable.
(i) A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane.
(j) A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane. ‡ Parts 83-90 of Title 33 Code of Federal Regulations.
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of August 12, 2024. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.