🔍 Key Concepts

• Fixed bridge channel marking lights per U.S. Aids to Navigation System • Difference between channel centerline/range lights and pier/obstruction lights • How left descending bank (LDB) and right descending bank (RDB) are marked on rivers

💭 Think About

• For each option, ask yourself: Does this pattern help a mariner FIND and STAY IN a marked channel under the bridge, or does it mark something else? • Think about which light patterns are used to mark the safe line of passage (center of the channel) versus just showing the edges or structures. • Recall which color combinations typically define the limits of the navigable span on rivers where banks are called left and right descending.

✅ Before You Answer

• For each choice, decide: Is this marking the centerline/range of a navigable channel under the span, or only the structure/edges? • Verify which colors (red vs green vs white) are normally associated with safe channel alignment under bridges versus general obstruction/pier marking. • Check whether a pattern of three white vertical lights is standard for indicating a navigational channel under a fixed bridge in U.S. inland waters.