Which lights are used to indicate channel boundaries on a single span bridge at night?

The correct indication of channel boundaries at night for a single span bridge is represented by two red lights on both sides of the span. This signaling is crucial for navigational safety, as it visually communicates to mariners the location of the bridge and the navigable passage beneath it.

Red lights are universally recognized as warning signals in maritime navigation, and their placement on both sides of the bridge aids boat operators in positioning their vessels correctly in relation to the bridge and ensuring safe passage under the structure. The presence of two red lights reinforces the boundaries of the channel, guiding vessels safely away from the navigational hazards associated with the bridge.

In contrast, green lights are typically used to indicate the right side of a channel when approaching from seaward, while amber lights may signal caution or indicate specific conditions but are not standard for channel boundary indication. Flashing white lights serve different purposes such as marking important navigation points or indicating certain types of hazards, but they do not specifically denote channel boundaries in the context of a bridge.