Lights & Shapes — Cheat Sheet

A power-driven vessel underway shows sidelights, a sternlight and a forward masthead light. A second masthead light, aft and higher, is required at ≥50 m and permitted below 50 m. Below 12 m, an all-round white light plus sidelights is an alternative. Below 7 m with maximum speed ≤7 knots, the all-round white alternative requires sidelights if practicable. Hovercraft and WIG have additional mode-dependent signals.

For ordinary towing astern, the tug shows two masthead lights vertically, or three when the tow exceeds 200 m, plus sidelights, sternlight and a yellow towing light above it. Tow length is measured from the tug’s stern to the tow’s after end. Above 200 m, tug and tow show diamonds. Rule 24 also specifies the aft masthead light, pushing, rigid composite units, towed objects and assistance exceptions; select the corresponding display.

Under sail, show sidelights and a sternlight; below 20 m these may be combined in one tricolour lantern at or near the masthead. Optional red-over-green all-round lights must never accompany that tricolour. Below 7 m, use the prescribed sailing lights if practicable; otherwise keep a white torch or lighted lantern ready and show it in time to prevent collision. A vessel under sail also propelled by machinery is power-driven and shows a cone apex down by day.

Fishing status requires gear that restricts manoeuvrability. Trawling means dragging a dredge net or other fishing apparatus through the water: green over white all-round lights; other fishing: red over white. The day shape is two cones apex to apex. Add sidelights and sternlight when making way through water. Non-trawling gear extending horizontally >150 m requires a white all-round light or upward-pointing cone in the gear’s direction. Trawlers also follow 26(b)(ii) for the masthead light.

NUC means inability to manoeuvre as the rules require because of an exceptional circumstance; RAM results from the nature of the work. NUC shows two red all-round lights and two balls; RAM normally red-white-red and ball-diamond-ball. Their additional making-way lights differ. Dredging, diving and mine clearance have specific provisions. Rule 27(g) exempts vessels below 12 m from this rule’s lights and shapes except those engaged in diving.

A power-driven vessel is constrained by draught when its draught relative to the available depth and width severely restricts deviation from its course. In addition to Rule 23 lights, it may show three red all-round lights vertically, or a cylinder by day. These additional signals are optional under Rule 28.

On pilotage duty, show white over red all-round lights. When underway, add sidelights and sternlight; when at anchor, retain white over red and add Rule 30 anchor lights or shape. Off duty, show the lights or shapes prescribed for a similar vessel of the same length.

At anchor, show a white all-round light forward and another lower at or near the stern; below 50 m, one where best seen is an alternative. Day shape: one black ball. Deck illumination is mandatory at ≥100 m and permitted below. Aground, add two red all-round lights; show three balls by day. Below 12 m, the extra aground signals are exempt. The below-7 m anchor exemption applies only outside channels, fairways, anchorages and their vicinity, and where other vessels do not normally navigate.