Part CBasic
Rule 20: Application of lights and shapes
Sets when lights and shapes must be shown and forbids confusing extra lights.
Detailed Explanation
(a) Part C applies in all weathers.
(b) Light rules apply from sunset to sunrise. During this time, no other lights unless they cannot be mistaken for COLREG lights, do not impair visibility/distinctive character, and do not interfere with look-out.
(c) Prescribed lights are also shown by day in restricted visibility and may be shown in other circumstances if needed.
(d) Shape rules apply by day.
(e) All specified lights/shapes must comply with Annex I.
Key Points
- Lights: sunset to sunrise and reduced visibility
- No other lights that could mislead or impair detection
- Shapes displayed by day for same statuses
Examples
- At sunset you switch on navigation lights for your cargo ship even though visibility is still good. Rule 20(a) requires lights from sunset to sunrise regardless of conditions.
- A fishing vessel adds a powerful deck light for working at night. Rule 20(b) says additional lights must not be mistaken for required navigation lights or impair their visibility.
Common Mistakes
- Switching off navigation lights at dawn while still in restricted visibility.
- Installing decorative or commercial lighting that can be confused with required navigation lights.
- Displaying shapes at night or lights by day when the rule does not require them, causing confusion.