What does this traffic sign mean?

This sign indicates the presence of overhead electrical wires, usually for trams or trains. Because of this, rail traffic always has priority at this crossing, meaning you must yield to any approaching rail vehicles. Additionally, you are required to always wait when a rail vehicle is coming to ensure safety. This combination of rules helps prevent accidents at crossings with electrically powered rail vehicles. Remember, trams and trains cannot stop quickly, so you must be especially cautious and stop in time.