Rule 24 · USCG Navigation Rules
Vessel towing astern (tow over 200 m)
Three masthead lights in a vertical line, the yellow towing light aft — and a diamond shape by day on tug and tow.
Viewpoint
Display
Drag to orbit freely, scroll or pinch to zoom — or use the viewpoint buttons above (keyboard friendly).
From the port bow you see:
- white — Masthead light (top of three = tow > 200 m)
- white — Masthead light (middle of three)
- white — Masthead light (bottom of three)
- red — Port sidelight
→ Vessel towing astern (tow over 200 m) — Tow > 200 m, seen from the port bow.
Memory aid
“Three whites — long line: over 200 m of tow. Diamond by day at both ends.”
What it means
Tow > 200 m
Three whites in a vertical line replace the two of a short tow. Both the towing vessel and the tow display a diamond where it can best be seen by day.
Day shapes
Diamond
A diamond shape where it can best be seen — the mark of a tow over 200 m.
Light details
| Light | Colour | Arc | Position |
|---|---|---|---|
| Masthead light (top of three = tow > 200 m) | white | 225° forward | Mast, vertical line (top) |
| Masthead light (middle of three) | white | 225° forward | Mast, vertical line (2nd from top) |
| Masthead light (bottom of three) | white | 225° forward | Mast, vertical line (3rd from top) |
| Port sidelight | red | 112.5° to port | Port side, deck level |
| Starboard sidelight | green | 112.5° to starboard | Starboard side, deck level |
| Sternlight | white | 135° aft | Stern |
| Yellow towing light, above the sternlight | yellow | 135° aft | Aft, raised above the stern |
2D profile
Labelled side view — works without WebGL and in print. Variant shown: Tow > 200 m.
In fog, she sounds
Don’t confuse with…
Official source
Rule 24, reproduced from the public-domain COLREGs Rule 24(a) — USCG Navigation Rules. Diagrams and 3D scenes are original to boatrules.com.