How much higher must the after masthead light be compared to the forward masthead light on a power-driven vessel?

The correct answer is that the after masthead light on a power-driven vessel must be at least 2 meters higher than the forward masthead light. This requirement is based on the COLREGs (International Regulations for Preventing Collisions at Sea), which specify the arrangement of lights on power-driven vessels to ensure that they are easily distinguishable by other vessels.

The height difference is crucial for several reasons. First, it helps to clearly indicate the vessel's direction and heading to other mariners. The increased height of the aft masthead light ensures that it can be seen over other structures or obstructions on the vessel and helps to reduce confusion. By having the aft light positioned higher, it provides a clear visual cue that distinguishes the orientation and operating status of the vessel, which is essential for collision avoidance.

This requirement is specifically designed to enhance visibility and improve safety on the waters, making sure that vessels are appropriately recognized and identified at a distance. In practice, this height difference translates to the aft masthead light being installed at least 2 meters above the forward masthead light to maintain compliance with the regulations and promote safe navigation.