🔍 Key Concepts

• IALA Buoyage System Region B as adapted for the U.S. Aids to Navigation System • Meaning of a preferred-channel mark and how it differs from a simple lateral mark • Special light rhythm composite group flashing (2 + 1) and why a more complex rhythm is used

💭 Think About

• Think about when mariners most need extra information about which way the main or preferred channel continues. • Ask yourself: is composite group flashing (2 + 1) used to say "left" or "right" only, or is it used to say something more specific about a choice of channels? • Consider how light characteristics help distinguish a buoy that marks a junction or bifurcation from ordinary red or green lateral marks.

✅ Before You Answer

• Verify how a preferred-channel buoy is defined in the U.S. Aids to Navigation System (appearance, color pattern, and purpose). • Confirm which light characteristics are used on ordinary lateral buoys versus buoys at a bifurcation or junction. • Check whether composite group flashing (2 + 1) is ever restricted to only "left" or only "right" bank identification, or if it serves a different function.