Important information:

The German Ministry of the Environment has introduced environmental zones in certain German cities.

All vehicles entering these zones must now display a sticker indicating the Emission class of the vehicle. For vehicles NOT displaying such a sticker, the driver may be subject to a fine of €40.00. This ruling applies to all German licensed vehicles and also to all foreign vehicles that are licensed outside Germany.

All Hertz cars from Germany and Switzerland carry this stickers, however, Hertz cars rented outside Germany and Switzerland and driven into this two countries do not carry a sticker.
 
Therefore, Hertz customers renting outside Germany and wishing to drive into Germany and Switzerland and who enter a restricted zone, may be subject to the €40.00 fine.

The restricted zones can be identified by signs which are displayed at the point of entry to a restricted zone.