Part C — Lights and shapes

COLREGs Rule 20: Application of Part C

Rule 20 says navigation lights must be shown from sunset to sunrise and in restricted visibility by day, that no other lights may be shown which could be mistaken for them, and that day shapes are shown by day.

What Rule 20 says

  1. The rules in Part C apply in all weathers.
  2. Lights are shown from sunset to sunrise, and no other lights may be shown that could be mistaken for them, impair their visibility or distinctive character, or interfere with a proper look-out.
  3. Lights shall also be shown from sunrise to sunset in restricted visibility, and may be shown in any other circumstances where it is necessary.
  4. Shapes are shown by day.
  5. The lights and shapes must meet Annex I (positioning and technical details).

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

Switch the nav lights on at sunset and whenever visibility closes in by day. Bright deck lights or a cockpit torch can hide your nav lights and destroy your look-out's night vision.

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 C