The sign you mentioned, "Toll obligation according to the Federal Trunk Road Toll Act," indicates that vehicles must pay a toll to use the specified road, which is usually a federal highway. This applies primarily to trucks and commercial vehicles over a certain weight limit.

The purpose of the toll is to help maintain and improve road infrastructure. Drivers are typically required to pay the toll at designated toll booths, via electronic systems, or through pre-paid toll accounts, depending on the specific regulations and setup of the road network.

It's important for drivers to be aware of these toll obligations to avoid fines and ensure compliance with traffic regulations while traveling on federal highways in Germany. If you have any further questions about this sign or related traffic rules, feel free to ask!