What configuration of lights is displayed by a vessel towing a vessel alongside?

A vessel that is towing another vessel alongside must display specific lights to ensure that other vessels can identify its navigation status. When a vessel is towing another vessel, it indicates this by displaying two towing lights in a vertical line. This configuration helps mariners recognize that the towing vessel is engaged in a specific operation involving another vessel alongside it.

The two towing lights are typically bright white lights, positioned one above the other. This arrangement clearly signifies to nearby vessels that the towing operation is occurring, as well as allowing other vessels to assess the length and position of the tow without confusion. By using this distinctive light setup, the towing vessel adheres to the requirements set forth in the COLREGs, facilitating safe navigation on the water.

Choosing the other options would not correctly represent the lighting configuration required for a vessel towing another vessel alongside. Sidelights and a sternlight would not provide the necessary indication of towing status, and combinations of all-round lights do not specifically denote a towing situation in the manner required by navigation rules. Thus, the correct choice highlights the importance of clarity in signaling during towing operations.