IALACOLREG
10

Traffic Separation Schemes

Vessels using traffic separation schemes shall proceed in the appropriate traffic lane in the general direction of traffic flow.

Rule 10 applies to traffic separation schemes adopted by the IMO.

a
A TSS does not replace the rest of COLREG. It adds routeing discipline on top of the other collision rules.
b
A vessel using the scheme shall:
  • 1proceed in the appropriate traffic lane in the general direction of traffic flow
  • 2keep clear of the traffic separation line or separation zone so far as practicable
  • 3normally join or leave a lane at its termination, or otherwise at as small an angle to the traffic flow as practicable
c
If obliged to cross traffic lanes, a vessel shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
d
Vessels of less than 20 metres, sailing vessels and vessels engaged in fishing shall not impede the safe passage of a power-driven vessel following a traffic lane.
e
An inshore traffic zone should not be used when a vessel can safely use the adjacent lane, except where the vessel is under 20 metres, sailing, fishing, bound to or from a port or offshore installation within the zone, or avoiding immediate danger.
f
A vessel should avoid anchoring in a traffic separation scheme or its separation zones except in an emergency.
g
Fishing vessels shall not impede any vessel following a traffic lane.

STCW Bridge Watch Lens

1

In confined waters, think in terms of not impeding the vessel that is constrained by the channel or the traffic lane, then manoeuvre early to stay clear.

2

Build the traffic picture with sight, hearing, radar/ARPA and chart context. Do not let AIS or one isolated bearing replace systematic observation.

3

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

1

Start every scenario by classifying the encounter: overtaking, head-on, crossing, narrow channel, traffic separation, or restricted visibility.

2

If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.

3

Questions on channels and TSS often test the difference between 'keep out of the way' and 'shall not impede'. Read that wording carefully.

Key Takeaways

1

Use the lane in the direction of traffic flow and stay clear of the separation line or zone

2

Cross lanes only when necessary and do it as nearly as practicable at right angles

3

The wording 'shall not impede' is central for small craft, sailing craft and fishing vessels in a TSS

4

Inshore traffic zones are not a shortcut for larger ships when the main lane can be used safely

Common Mistakes

Joining or leaving a lane at a wide angle that confuses traffic

Treating the inshore traffic zone as a convenience lane instead of a limited-use area

Anchoring inside the scheme when there is no emergency

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