What does the German road sign marked “Umweltzone” identify?

The German road sign marked “Umweltzone” identifies an environmental zone.

Umweltzone is German for “environmental zone,” commonly translated in traffic contexts as a low-emission zone. These areas restrict access for vehicles that do not meet specified emissions standards. The policy is intended to reduce harmful urban air pollution, especially concentrations of particulate matter and nitrogen oxides.

Vehicles entering a German environmental zone generally need an appropriate emissions sticker, known as an Umweltplakette, displayed on the windscreen. The sticker color corresponds to the vehicle’s emissions classification. A green sticker is the normal requirement in many established zones, although local rules and exemptions can differ.

The sign is sometimes confused with a general “green” sustainability symbol or with a toll-road notice. It is specifically a traffic-access restriction based on vehicle emissions. Drivers should check the local rules before entering, because exemptions, enforcement, and permitted vehicle categories are controlled by the relevant German authority.