Rule 28
Vessel constrained by their draught
A vessel constrained by her draught may, in addition to the lights prescribed for power-driven vessels in rule 23, exhibit where they can best be seen three all-round red lights in a vertical line, or a cylinder.
Rule 28 of the COLREGs addresses “vessels constrained by their draught.” This rule applies to ships with limited maneuverability due to their draught and the available depth of water. In other words, such vessels find it difficult to change course quickly or execute tight turns. This constraint is especially critical in shallow waters, narrow channels, or busy shipping lanes, where rapid course changes are needed to avoid collisions or other hazards.
A vessel constrained by its draught (CBD) must primarily display the following lights:
- Three (3) all-round red lights in a vertical line.
In addition to these, the vessel must also exhibit the standard navigational lights required for power-driven vessels, which include:
- Sidelights
- A stern light, and
- One or more masthead lights
During the daytime, a CBD vessel must exhibit:
- a single black cylinder
Refer to the figure below for a visual representation of the requirements.
Figure 1.A vessel constrained by her draft displaying 3 all-round red lights at night.
Although large ships, such as those carrying significant cargo, often meet the criteria for being CBD, the classification is not solely based on size. Even medium-sized vessels may be considered CBD if operating in shallow waters where their ability to maneuver is significantly limited.