Module 5 - COLREGs
Rules 9 & 10 — Narrow Channels and TSS
What you will learn
Plan a narrow-channel or traffic-lane passage that obeys the routeing rule without assuming channel-confined or lane-following traffic is exempt from the other collision rules.
Rules 9 and 10 protect predictable traffic flow and sea room. They add 'do not impede' duties, but the lookout, risk, action and in-sight or restricted-visibility rules continue to apply.
Rule 9 requires a vessel proceeding along a narrow channel or fairway to keep as near the starboard outer limit as is safe and practicable. A vessel under 20 metres or a sailing vessel must not impede a vessel that can safely navigate only within the channel. A vessel must not cross if the crossing would impede such a vessel, and overtaking or bend signals and local directions may also apply.
Rule 10 applies to IMO-adopted traffic separation schemes and does not relieve any vessel of another rule. A vessel using a lane proceeds in the general direction of traffic flow and normally joins or leaves at a lane termination; joining or leaving from a side is done at as small an angle to the traffic direction as practicable. A vessel should avoid crossing, but when obliged to cross does so on a heading—as distinct from course over ground—as nearly as practicable at right angles to the general traffic flow.
Vessels following a traffic lane do not automatically have priority over crossing vessels. The ordinary steering and sailing rules still decide collision encounters. At the same time, a sailing vessel or vessel under 20 metres must not impede the safe passage of a power-driven vessel following the lane, so the crossing should be planned early enough not to force lane traffic to deviate course or speed.
The Inshore Traffic Zone rule has explicit categories and purposes. Vessels under 20 metres, sailing vessels and vessels engaged in fishing may use it; other vessels may use it for the listed access purposes or immediate danger. Do not turn the general 'use the lane when safe' wording into a blanket ban on small-yacht ITZ use, and check current chart notes and MCA routeing guidance for the particular scheme.
Plan a cross-tide TSS crossing
A yacht must cross a traffic lane in a strong tidal stream, with two ships following the lane several miles apart.
1. Select the gap
Assess the ships systematically and delay or adjust the crossing point so the yacht will not impede their safe passage.
2. Set the heading
Steer a heading as nearly as practicable at right angles to the traffic flow; accept that tide may make the course over ground oblique.
3. Keep applying COLREGs
Maintain lookout and safe speed, reassess risk and use the appropriate crossing or restricted-visibility rule if an encounter develops.
Sense check: A chartplotter track at 90° achieved by crabbing the bow up-tide is not what Rule 10(c) asks for; the rule specifies heading.
Common mistake or limitation
- Being established in a traffic lane does not make a vessel automatically stand-on in every encounter.
- The right-angle requirement refers to heading, not course over ground; strong tide can make those directions visibly different.
Recap
- Rules 9 and 10 protect traffic flow while preserving every other applicable collision duty.
- Do-not-impede obligations require early planning before collision risk develops.
- Check the actual charted scheme, local directions and current MCA guidance rather than applying a generic lane diagram blindly.
Optional quick check
Section 8 of 9
In strong cross-tide, how should a yacht cross an IMO-adopted traffic lane when obliged to do so?
Continue studying COLREGs
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