Environmental stickers must be affixed to the car so that they are clearly visible. But where exactly do the different stickers have to be affixed? Just as the rules for environmental zones differ from country to country, so do the ways in which the stickers must be affixed to the car.
The German green environmental sticker must be affixed to the windscreen from the inside. It does not matter whether the sticker is affixed on the left or right. However, it must always be clearly visible. If the sticker is placed too high and thus in the tinted upper edge of the windscreen, it can no longer be easily seen from the outside. Many people stick the sticker in the lower corner of the passenger side, as it does not restrict the driver's field of vision there and can also be easily seen by the officers from the pavement in the event of a check.
The same applies to the Austrian sticker, i.e. the Pickerl, and the French sticker. Like the German environmental sticker, they too must be affixed to the inside of the windscreen. Here, too, neither a side nor the height is specified. But beware! Since the French sticker is also obligatory for motorbikes, it has two adhesive sides. For cars, the front adhesive layer should be removed so that the sticker can be stuck to the windscreen from the inside. This way it is also much better protected against the weather and lasts longer. For motorbikes, the foil on the back of the sticker can be removed so that the sticker can be attached to the body of the motorbike.
Care must also be taken with the German E-sticker, which foreign vehicles can get in order to take advantage of e-cars on German roads. It has to be stuck to the outside of the rear window! There is no official explanation as to why this is so. Presumably, this makes it easier for the police to see from behind whether a vehicle is actually an e-car and is allowed to drive in a bus lane, for example.
By the way, the stickers are designed to be non-transferable and to break when removed. However, this also means that the first attempt at sticking them on must be successful! Together with the toll stickers of the various countries, which, unlike the environmental stickers, have to be bought anew every year, there are dozens of stickers. A windscreen can become a real sticker collection.