A low-emission zone (Umweltzone) is an area where high-emission vehicles are banned. Your vehicle must have an Umwelt-Plakette to drive there.
Diesel vehicles are banned from low-emission zones in some cities.3 Motorcycles are always allowed in low-emission zones.
In Berlin, the area inside the Ringbahn is a low-emission zone.1 Other German cities also have low-emission zones.2

Sources and footnotes
-
Wikimedia Commons (2013) ⤴
-
ADAC (2025), bussgeldkatalog.org (2026) ⤴