Of the 145 pages of content included in A Guide to the International and Inland Navigation Rules, view the following six pages from the all-important module on Light Configurations and Day Shapes to get a feel for the uniquely simplified presentation and user-friendliness of A Guide to the International and Inland Navigation Rules.

A Guide to the International and Inland Navigation Rules

Learning Objectives

In this module, you will learn all of the light configurations and day shapes required by the Rules.

Specifically, this module covers the requirements for:

• power-driven vessels underway,
• special types of power-driven vessels,
• vessels towing and pushing,
• vessels being pushed ahead or towed alongside,
• vessels being towed or pushed,
• inconspicuous vessels or objects being towed,
• sailing vessels underway,
• vessels under oars,
• vessels engaged in fishing and trawling,
• vessels not under command,
• vessels restricted in their ability to maneuver,
• vessels engaged in dredging or underwater operations,
• vessels engaged in diving operations,
• vessels engaged in mine clearing operations,
• vessels constrained by their draft,
• pilot vessels, and
• anchored vessels and vessels aground.

Module 8: Light Configurations and Day Shapes

Power-driven Vessels Underway >= 50 Meters  – Rule 23

If a power-driven vessel underway is equal to or greater than 50 meters long, it must display:

• 2 Masthead lights, one forward and the other, placed higher, abaft,
• sidelights, and
• a sternlight.

“Underway” is defined as a vessel that is not at anchor, or made fast to the shore, or aground.

Power-driven Vessel, Underway, >=50 Meters

Great Lakes Only
On the Great Lakes, a power-driven vessel greater than 50 meters long may use an all-round white light in place of both a rear masthead light and a sternlight.

This rule recognize the fact that a rear masthead light, which projects forward, and a sternlight, which projects aft, are the functional equivalent of an all-round light.

Power-driven Vessel, Underway, >=50 Meters, Optional All-around

Module 8: Light Configurations and Day Shapes

Power-driven Vessels Underway < 50 Meters – Rule 23

If a power-driven vessel underway is less than 50 meters long, it is not required to display a masthead light abaft, but it may do so.

Power-driven Vessel, Underway, <50 Meters

Power-driven Vessel, Underway, <50 Meters, Optional Masthead Light

Module 8: Light Configurations and Day Shapes

Rigidly Connected Composite Units – Rule 24

If a pushing vessel and a vessel being pushed ahead are rigidly connected as a composite unit, then they must use the lights required for power-driven vessels underway.

Rigidly Connected Composite Unit, >=50 Meters

Module 8: Light Configurations and Day Shapes

Smaller Power-Driven Vessels – Rule 23

Smaller power-driven vessels are subject to less extensive light configuration requirements. Specifically, if a power-driven vessel is less than 12 meters long, it may display an all-round white light and sidelights.

Power-driven Vessel, <12 Meters, Optional All-around White Light

Inland Only
The above, less-extensive requirement is extended to vessels up to 20 meters long.

Recall from Module 7 that, on a vessel less than 20 meters long, the sidelights may be combined in one lantern placed on the centerline of the vessel.

International only
A power-driven vessel less than 7 meters long and underway at less than 7 knots may display only an all-round white light if it is impracticable to display sidelights.

Power-driven Vessel, Underway, <7 Meters <7 Knots, Sidelights Not Impracticable, Optional All-around White Light

Power-driven Vessel, Underway, <7 Meters <7 Knots, Sidelights Impracticable, All-around White Light

International only
In addition, the masthead light or all-round white light on a vessel less than 12 meters long may be off the centerline if centerline fitting is not practicable.  But, in this case, the sidelights must be combined in one lantern, and they must be on the centerline or as near as possible to the fore and aft line of the masthead or all-round white light.

Power-driven Vessel, Underway, <12 Meters, Centered Sidelights Impracticable, One Sidelights Lantern

Module 8: Light Configurations and Day Shapes

Special Types of Power-driven Vessels – Rule 23

Certain lights are required on special types of power-driven vessels. These lights are required in addition to those required for power-driven vessels underway. 

Nautical Note: A WIG is a vessel that is capable of flying near the water’s surface.

If it is impracticable for a seaplane or a WIG craft to exhibit lights and shapes of the required characteristics or in the required positions, she must exhibit lights and shapes as closely similar in characteristics and position as is possible.

Hovercraft in displacement mode

Hovercraft in non-displacement mode

 Submarine

International only: WIG

Inland only: Law enforcement vessel engaged in law enforcement of public safety activities

Inland only: Vessel engaged in government sanction activities – may be commercial