What does this traffic sign indicate?

This traffic sign indicates the direction to a specific tram line, which in this case is tram line number 3 (U3). In Germany, signs like this are used to help drivers and pedestrians navigate to public transportation. The yellow background and the capital 'U' signify that it relates to the underground (U-Bahn) or tram services.

Understanding such signs is important for proper navigation and ensuring that you can easily find and access public transport options, which is a vital part of urban traffic management. Familiarity with these signs ensures compliance with local rules, enhancing safety and efficiency in traffic flow.