Question 25 OSV01 - Master/Chief Mate - Offshore Supply Vessels

The Correct Answer is B **Explanation for Option B (Correct Answer):** The placement requirements for navigation lights, including the masthead light, are detailed in the International Regulations for Preventing Collisions at Sea (COLREGs), which are adopted for inland waters unless specifically superseded. Rule 23 (Power-driven vessels underway) describes the required lights. The exception for the placement of the masthead light relative to the fore and aft centerline is specifically granted to smaller vessels. Annex I, Section 3(b) of COLREGs (which deals with the positioning and technical details of lights) states: * "On a vessel of less than 12 metres in length the masthead light or all-round light may be displaced from the fore and aft centreline if required for practical reasons, provided that the sidelights are combined in one lantern which is carried on the fore and aft centreline of the vessel or is placed as nearly as practicable to the fore and aft centreline." Therefore, vessels **less than 12 meters in length** have the regulatory allowance to place the masthead light (or all-round light) off-center due to practical constraints. **Explanation of Incorrect Options:** **A) which has separate sidelights carried on the outboard extremes of the vessel's breadth:** This condition describes a standard setup for many vessels, particularly larger ones. Having separate sidelights carried outboard does not, by itself, grant permission to displace the masthead light from the fore and aft centerline. The displacement exception is tied to the vessel's overall length (less than 12m), not the configuration of the sidelights alone. **C) engaged in fishing:** Vessels engaged in fishing (Rule 26) have special signal lights (green over white all-round lights), but their standard masthead light (required when making way and not fishing) or other required lights must still adhere to the standard placement requirements unless they fall under the length exception (less than 12m or less than 20m with certain restrictions, but the primary exception for practical off-center placement is less than 12m). The vessel's activity does not override the structural placement rules for standard lights. **D) less than 20 meters in length:** While vessels less than 20 meters have simplified lighting requirements (e.g., they may carry an all-round white light instead of separate masthead and stern lights if less than 12m, or may combine sidelights), the specific regulatory relief allowing the *masthead light* to be placed off the fore and aft centerline for practical reasons is limited to vessels **less than 12 meters in length** (Annex I, Section 3(b)). Vessels between 12m and 20m must generally adhere to the centerline placement rule for their masthead light.