What is the indicator of a drawbridge when it is in operation to allow vessels to pass?

When a drawbridge is in operation to allow vessels to pass, it typically displays a flashing yellow light. This signal is an important indicator for both vessel operators and land traffic. The flashing yellow light alerts all approaching vessels that the drawbridge is in the process of being raised or is already raised, signifying that it is safe for vessels to proceed.

This system is designed to prevent confusion and enhance safety on the waterway and roadways nearby. In contrast, the other light signals serve different purposes: a green light often indicates that a drawbridge is open to road traffic, a red light indicates that the bridge is closed to traffic, and a white light may be used for other navigational or operational purposes, but not specifically to indicate that a drawbridge is open to water traffic. Understanding these signals is crucial for safe navigation around drawbridges.