What does a red and green lateral marker indicate?

The red and green lateral marker serves a specific purpose in navigational systems, primarily to indicate safe passage for vessels. When you encounter a red and green lateral marker, it typically means that the marker is part of a system where both colors represent different characteristics of navigation. Specifically, these markers often indicate that vessels may navigate freely, with no restrictions on which side to pass.

In many navigation systems, the red marker denotes that it is on the right side of the waterway when traveling upstream, while the green marker indicates the left side. Since the question refers to the ability to pass them, the implication is that when navigating within a marked channel, a vessel can safely choose either side to pass. This flexibility is essential for facilitating smooth traffic flow and ensuring that all vessels can navigate safely without getting stranded or colliding.

The option suggesting restrictions on where to pass, or that the marker is only for downstream navigation, does not accurately describe the function of red and green lateral markers, as their primary role is to guide vessels in both directions safely through channels.