Rule 10: traffic separation schemes.

What does COLREGs Rule 10 say?

It sets out how to behave in and around traffic separation schemes: how to use a lane (10(b)), how to cross one (10(c)), who may use an inshore traffic zone (10(d)), when you may enter a separation zone (10(e)), caution near the ends of a scheme (10(f)), anchoring (10(g)), keeping well clear if you are not using it (10(h)), who must not impede vessels in a lane (10(i) and (j)), and exemptions for certain vessels restricted in their ability to manoeuvre (10(k) and (l)).

Which schemes does Rule 10 apply to?

Rule 10(a) says it applies to traffic separation schemes 'adopted by the Organization'. It sits in Part B, Section I, so it applies in any condition of visibility, and Rule 19(c) requires due regard to restricted visibility when complying with it.

Does a vessel in a traffic lane have right of way?

Not in general. Rule 10(a) says the rule 'does not relieve any vessel of her obligation under any other rule', so the rest of Part B applies inside a scheme as it does outside. Vessels in sight of one another follow Section II as anywhere else (see Rule 15, Crossing situation); in restricted visibility, Rule 19 applies.

The exceptions are specific: under 10(i) and 10(j), vessels engaged in fishing, vessels of less than 20 metres and sailing vessels must not impede certain vessels following a lane. Those are 'not to impede' duties, so Rule 8(f) applies to them.

How do you use a traffic lane — Rule 10(b)?

A vessel using a scheme proceeds in the appropriate lane in the general direction of traffic flow for that lane; keeps clear of the separation line or separation zone so far as practicable; and normally joins or leaves at the end of the lane. If she joins or leaves from the side, she does so at as small an angle to the general direction of traffic flow as practicable.

How should you cross a traffic separation scheme?

Rule 10(c): avoid crossing traffic lanes so far as practicable, but if you are obliged to cross, do so 'on a heading' as nearly as practicable at right angles to the general direction of traffic flow.

The rule says heading, not track. With a tidal stream setting you along the lane, you keep your heading at right angles and accept that your track over the ground is not. As we read it, the point is that vessels in the lane then see an unmistakable crossing aspect.

When can you enter a separation zone?

Under 10(e), a vessel other than one crossing, or joining or leaving a lane, shall not normally enter a separation zone or cross a separation line except in an emergency to avoid immediate danger, or to engage in fishing within the separation zone.

What about the ends of a scheme, anchoring, and vessels not using it?

Rule 10(f): navigate with particular caution in areas near the terminations of a scheme. Rule 10(g): avoid anchoring in a scheme or near its terminations, so far as practicable. Rule 10(h): a vessel not using a scheme shall avoid it 'by as wide a margin as is practicable'.

Who can use an inshore traffic zone?

Rule 10(d)(i): a vessel shall not use an inshore traffic zone when she can safely use the appropriate lane in the adjacent scheme. Vessels of less than 20 metres, sailing vessels and vessels engaged in fishing may use it.

Rule 10(d)(ii): any vessel may use it when en route to or from a port, offshore installation or structure, pilot station or other place within the inshore traffic zone, or to avoid immediate danger.

Who must not impede vessels in a traffic lane?

Under 10(i), fishing vessels must not impede any vessel following a lane. Under 10(j), vessels under 20 metres and sailing vessels must not impede the 'safe passage' of a power-driven vessel following a lane.

Note the difference: 10(i) protects any vessel following a lane; 10(j) protects a power-driven vessel. Neither forbids fishing or sailing in a lane — they forbid impeding.

Which vessels are exempt from Rule 10?

Two kinds of vessel restricted in her ability to manoeuvre, and only to the extent necessary to carry out the operation: under 10(k), one engaged in maintaining safety of navigation in a scheme; under 10(l), one laying, servicing or picking up a submarine cable within a scheme.

How might Rule 10 come up in an MCA oral?

It may come up as a passage-planning question or a crossing scenario. Examples of the kind of question to be ready for:

“You need to cross a traffic separation scheme. How do you do it, and why that way?”

“There's a strong tide setting along the lane. What do you steer?”

“You're in the lane and a power-driven vessel is crossing from your starboard side. Who gives way?”

“On a 15-metre sailing yacht, can you use the inshore traffic zone? Could a 60-metre motor yacht?”

“When may you enter the separation zone?”

Where do candidates go wrong on Rule 10?

The common slips: treating a vessel in the lane as stand-on over everyone; crossing on a track at right angles rather than a heading; joining or leaving from the side at a broad angle; using the inshore traffic zone as a through route when the lane could safely be used; and forgetting that a vessel not using a scheme must avoid it by as wide a margin as practicable.