Which motor vehicles are allowed to use a road with this sign?

The sign you've shown indicates an "Environmental Zone" (Umweltzone) in Germany. This area is designated to reduce air pollution, and access is restricted based on vehicle emissions.

The upper sign shows the environmental zone, while the lower sign indicates that certain vehicles are allowed to enter, depending on their emissions stickers.

Only vehicles that have the appropriate emissions sticker, which denotes their level of emissions, can legally enter this zone. Typically, this includes:

1. Vehicles with a green sticker (low emissions).
2. Vehicles with a yellow sticker (moderate emissions) may have restricted access, depending on specific local regulations.
3. Vehicles with a red sticker (higher emissions) are usually prohibited from entering the zone.

Thus, the correct understanding is crucial for compliance with local environmental regulations and to avoid fines.