What sound signal indicates the intention to leave on the port side in a crossing situation?

In a crossing situation, the intention to leave on the port side is communicated by one short blast of the horn. This sound signal is part of the International Regulations for Preventing Collisions at Sea (COLREGs), which establish standards for navigational practices and sound signals to promote safety and clarity among vessels.

One short blast indicates that a vessel intends to alter its course to starboard, which means that the bow of the vessel will move to the right as viewed from the stern. When two vessels are approaching each other and one vessel makes one short blast, it is understood that the vessel making the signal intends to pass the other vessel on its port side, thereby indicating its intended course of action clearly.

This helps to prevent misunderstandings during potentially perilous crossing situations, facilitating safe navigation and ensuring that both vessels can proceed without confusion as to each other’s intentions.