Part B · Section I

COLREGs Rule 10: Traffic separation schemes

Rule 10 says vessels using a traffic separation scheme follow the lane in the general direction of traffic, join and leave at the ends, and cross, if they must, on a heading as near as possible to a right angle to the traffic flow.

What Rule 10 says

  1. Proceed in the appropriate lane in the general direction of traffic flow, keep clear of the separation line or zone, and join or leave at the ends of the lane. Joining or leaving from the side should be at as small an angle as practicable.
  2. Avoid crossing lanes. If you must cross, do so on a heading as nearly as practicable at right angles to the general direction of traffic flow.
  3. Through traffic that can safely use a lane should not use the inshore traffic zone. Vessels under 20 metres, sailing vessels and vessels fishing may use it.
  4. Do not enter a separation zone except to cross, in an emergency, or to fish within it.
  5. Take particular care near the ends of a scheme, and avoid anchoring in it or near its ends.
  6. A vessel not using a scheme should keep clear of it by as wide a margin as practicable.
  7. Vessels under 20 metres and sailing vessels shall not impede the safe passage of a power-driven vessel following a lane. Fishing vessels shall not impede any vessel following a lane.

This is a plain-English summary, not the official wording. For the exact text, see the IMO convention. In UK waters the rules are given legal force by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations.

What it means on a yacht

Crossing the Dover Strait or the Casquets TSS, hold a heading at 90° to the lanes even when the tide sets you sideways: it is your heading, not your track, that must be square. Motor if you cannot hold the heading and speed under sail.

Practise it

Test yourself on who gives way in the free COLREGs trainer, or print the rules of the road cheat sheets for the chart table.

Other rules in Part B

Frequently asked questions

Do you cross a TSS at right angles to the heading or the track?

The heading. Rule 10(c) requires your heading to be as near to 90° to the traffic flow as practicable, so you present your beam to ships and cross quickly, even if the tide makes your track over the ground diagonal.