COLREGs Rules of the Road Practice Exam — Prep & Study Guide

The light designed to show an arc of 135 degrees, with 67.5 degrees from each side of the vessel, is the stern light. This type of light is specifically used on powered vessels and is required by the COLREGs to indicate the location and movement of the vessel from behind. The stern light assists other vessels in understanding the position of the vessel, particularly at night or in poor visibility conditions.

In contrast, the masthead light is a white light placed at the highest point on the vessel that shows an arc of 225 degrees. The all-around light emits light in all directions, generally showing an arc of 360 degrees. A towing light is a special light that indicates a vessel that is towing another and operates under different visibility criteria. Each of these lights serves a distinct purpose and has specific regulations set forth by the COLREGs to ensure safe navigation and collision avoidance.