The sign indicating "End of a traffic restriction zone to reduce harmful air pollution in an area" signifies that you are leaving an area where specific driving restrictions were in place to improve air quality.

In Germany, these zones are implemented to tackle pollution, and vehicles that do not meet certain emission standards may be restricted from entering or traveling within those areas. When you see this sign, it means that the previous restrictions do not apply anymore and you are allowed to drive your vehicle without any limitations related to air quality regulations.

Always ensure to follow any additional signage or local regulations that may still apply even after leaving the restricted area. If you have any other questions, feel free to ask!