Question 720 Rules of the Road

The correct answer is C) 67.5°. The International and Inland Navigation Rules state that the stern light shall be positioned such that it will show from dead astern to 67.5 degrees on each side of the vessel. This is because the stern light is required to be visible over an arc of the horizon of 135 degrees, centered on the stern (67.5 degrees on each side of the vessel). The other options are incorrect because A) 135.0° is the total arc of visibility, not the angle on each side; B) 112.5° is the arc of visibility for the side lights, not the stern light; and D) 22.5° is too narrow an arc of visibility for the stern light.