What Do The Red And Green Lights On Ships Mean?

Modern shipping makes use of all manner of relatively new technologies, from using GPS for navigation to building dual-fuel engines in a bid to cut down on emissions. However, a number of key shipping conventions are still rooted in tradition. The red and green lights on ships are one such convention, as the two lights are used to distinguish a ship's port and starboard side. The term "starboard" can be traced back to Anglo Saxon seafarers, who tended to use a rudder hung on the right side of their boats for steering. The rudder was called the "steorbord," which eventually became the modern word, starboard. It's still used to describe the right hand side of a boat today, and many modern boats also still have steering wheels on the right.

Determining which side of a boat is the left and which is the right is fairly simple. If you're looking at a ship from the rear — that is, if it's sailing away from you — the right of the boat is on your right. If the ship is sailing towards you, the boat's right or "starboard" side is on your left. The other side of the boat — its left side — is called the "port" side. Of course, to work this out, you'll need to be able to see whether the boat is heading towards you or away from you, which in bad weather or in the dark, might not be possible. This is where the red and green lights come in.

A red light indicates the ship's port side and a green light indicates the ship's starboard side. These lights can be used in the dark or in low visibility conditions to quickly determine a ship's direction. If you're navigating a ship and you see another vessel displaying only a red light, it means you're viewing the ship's port side. That means it's crossing your path, from your right to your left. Seeing only a green light means that it's crossing your path from your left to your right. If you see both a red and a green light, that means that the vessel is travelling towards you. If you see only a white light coming from the ship's stern, it means the vessel is travelling away from you.

Using this straightforward lighting system makes it easy to work out where other ships in a busy area are heading, even if you can't see the ship clearly. That in turn makes it easier to determine if you need to adjust your course to leave space or avoid a collision. It's not just ships that use the lighting system either: the same red and green lights can also be found on airplanes and on helicopters, where they perform the same function.