Boat Massachusetts Handbook Home Page
Boat Massachusetts Handbook Home Page
Be on the lookout for the lights of other vessels when boating at night. Several types of lights serve as navigation aids at night. There are four common navigation lights.
Types of Nighttime Navigational Lights |
Illustrations |
Sidelights: These red and green lights are called sidelights (also called combination lights) because they are visible to another vessel approaching from the side or head-on. The red light indicates a vessel’s port (left) side; the green indicates a vessel’s starboard (right) side. Sternlight: A white light seen from behind or nearly behind the vessel. Masthead Light: This white light shines forward and to both sides and is required on all power-driven vessels. A masthead light must be displayed by all vessels when under engine power. The absence of this light indicates a sailboat under sail. All-Round White Light: On power-driven vessels less than 39.4 feet in length, this light may be used to combine a masthead light and sternlight into a single white light that can be seen by other vessels from any direction. This light serves as an anchor light when sidelights are extinguished. |
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Encountering Vessels at Night—What the Lights Mean |
Illustrations of Lights |
| When you see a white and a green light, you are the stand-on vessel. You should remain alert, however, in case the other vessel operator does not see you or does not know navigational rules. |  |
| When you see only a white light, you are overtaking another vessel or it is anchored. It is the stand-on vessel, whether underway or anchored. You may go around it on either side. |  |
| When you see a red and a white light, you must give way to the other vessel! Slow down and allow the vessel to pass, or you may turn to the right and pass behind the other vessel. |  |
| When you see a red, a green, and a white light, you are approaching another power-driven vessel head-on and both vessels must give way. |  |
| When you see a red and a green light but no white light, you are approaching a sailing vessel head-on and you must give way. |  |
| When you see only a green light or only a red light, you may be approaching a sailing vessel and you must give way. A sailing vessel is always the stand-on vessel except when it is overtaking or in a narrow channel. | See only a green light... |
See only a red light... |
