What does this traffic sign indicate?

This traffic sign warns drivers of a moveable bridge ahead, such as a drawbridge or bascule bridge. The sign indicates that the bridge may open to allow ships or boats to pass, so drivers should be prepared to stop and wait. It is important to reduce speed and be attentive to signals or barriers that control traffic when the bridge is in operation. This helps ensure safety by preventing vehicles from attempting to cross when the bridge is open.