Rule 27 · USCG Navigation Rules
Vessel restricted in ability to manoeuvre (RAM)
Red-white-red all-round lights in a vertical line and ball-diamond-ball by day; making way adds masthead lights, sidelights and sternlight.
Situation
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:
- All-round red (top)
- All-round white (middle)
- All-round red (bottom)
→ Vessel restricted in ability to manoeuvre (RAM) — Underway, not making way, seen from the port bow.
Memory aid
“Red, white, red — restricted ahead.”
What it means
Underway, not making way
The nature of her work (cable laying, dredging, surveying, replenishment…) — not a breakdown — keeps her from manoeuvring.
Making way through the water
Unlike a NUC, a RAM making way ALSO shows masthead light(s) with the sidelights and sternlight (a vessel of 50 m or more adds the second masthead light).
At anchor
At anchor she keeps the red-white-red and ball-diamond-ball AND adds the Rule 30 anchor light(s) and ball (50 m+ adds the second, lower anchor light aft). While working at anchor she still sounds the restricted-manoeuvrability fog signal.
Day shapes
Underway, not making way
Ball – diamond – ball
Ball, diamond, ball in a vertical line where they can best be seen.
Making way through the water
Ball – diamond – ball
Ball, diamond, ball in a vertical line where they can best be seen.
At anchor
Ball – diamond – ball
Ball, diamond, ball in a vertical line.
Anchor ball
One ball forward — the Rule 30 anchor shape, shown in addition.
Light details
Underway, not making way
| Light | Colour | Arc | Position |
|---|---|---|---|
| All-round red (top) | red | 360° all-round | Mast, vertical line (top) |
| All-round white (middle) | white | 360° all-round | Mast, vertical line (2nd from top) |
| All-round red (bottom) | red | 360° all-round | Mast, vertical line (3rd from top) |
Making way through the water
| Light | Colour | Arc | Position |
|---|---|---|---|
| All-round red (top) | red | 360° all-round | Mast, vertical line (top) |
| All-round white (middle) | white | 360° all-round | Mast, vertical line (2nd from top) |
| All-round red (bottom) | red | 360° all-round | Mast, vertical line (3rd from top) |
| Masthead light | white | 225° forward | Forward masthead position |
| 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 |
At anchor
| Light | Colour | Arc | Position |
|---|---|---|---|
| All-round red (top) | red | 360° all-round | Mast, vertical line (top) |
| All-round white (middle) | white | 360° all-round | Mast, vertical line (2nd from top) |
| All-round red (bottom) | red | 360° all-round | Mast, vertical line (3rd from top) |
| Anchor light (forward) | white | 360° all-round | Forward, centreline |
2D profile
Labelled side view — works without WebGL and in print. Variant shown: Underway, not making way.
In fog, she sounds
Don’t confuse with…
Official source
Rule 27, reproduced from the public-domain COLREGs Rule 27(b) — USCG Navigation Rules. Diagrams and 3D scenes are original to boatrules.com.