COLREGs · Rule 10 · 33 CFR §83.10
Traffic Separation Schemes
Conduct in IMO-adopted traffic separation schemes: proceed in the established direction of flow, keep clear of the separation zone or line, join or leave a lane at as small an angle as practicable.
What does Rule 10 actually say?#
Source
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Under Inland Rule 10, compliance with the Rule's requirements does NOT relieve a vessel of her obligations under which other authority?
How does Inland Rule 10 differ from COLREGs?#
Inland Rule 10 is structurally different — titled 'Vessel Traffic Services' (33 CFR §83.10), it requires compliance with a USCG-regulated VTS rather than an IMO-adopted TSS. The text addresses lane discipline within VTS-monitored waters.
21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.
Why it shows up on the exam#
Rule 10 governs conduct in a traffic separation scheme; it does not create right of way. The exam tests the geometry — join and leave at a small angle, cross at right angles — and the fact that Inland Rule 10 is a completely different rule about Vessel Traffic Services.
What does the exam actually test here?#
Using a lane
With the flow, clear of the zone
Proceed in the appropriate lane in the general direction of traffic flow, keep clear of a separation line or zone so far as practicable, and normally join or leave at the termination of the lane — or, from either side, at as small an angle to the flow as practicable.
Crossing
As near right angles as practicable
Avoid crossing traffic lanes so far as practicable, but where obliged to cross, do so on a heading as nearly as practicable at right angles to the general direction of traffic flow. Note it is the heading, not the track, that the rule specifies.
Not impeding
Fishing, under 20 m, sail
A vessel engaged in fishing shall not impede the passage of any vessel following a traffic lane, and a vessel under 20 metres or a sailing vessel shall not impede the safe passage of a power-driven vessel following a lane.
Rule 10 — common exam questions#
How should you cross a traffic separation scheme?
Avoid crossing if practicable; where you must cross, do so on a heading as nearly as practicable at right angles to the general direction of traffic flow (33 CFR §83.10(c)).
Who may use an inshore traffic zone?
A vessel should not use one when she can safely use the adjacent traffic lane, but vessels of less than 20 metres, sailing vessels, and vessels engaged in fishing may use it. Any vessel may use it en route to or from a port, offshore installation, pilot station, or other place within the zone, or to avoid immediate danger (33 CFR §83.10(d)).
Does Rule 10 give a vessel in a lane right of way?
No. Rule 10(a) says it does not relieve any vessel of her obligations under any other rule. What it does is forbid fishing vessels, vessels under 20 metres, and sailing vessels from impeding a vessel following a lane.
What is Inland Rule 10?
On inland waters Rule 10 is Vessel Traffic Services, not traffic separation schemes — the numbering matches but the subject does not. That is one of the handful of places where the two rule sets genuinely diverge.
Authoritative source#
- 33 CFR §83.10 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
- COLREGs Rule 10 is published by the IMO and is authoritative internationally.
Practise this rule against the real exam.
Real exam questions. No signup, no card.
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