In order to reduce air pollution, stickers and registrations can only be issued to vehicles that comply with the specified emission standards. However, there are various exceptions to the sticker and registration requirement. As with all other rules in the environmental zones, these vary greatly from country to country.
In Germany, a general sticker requirement applies only to cars and buses, as well as vans and trucks of various weight classes. Class L vehicles, which include motorbikes, scooters and quads, are generally not subject to the sticker requirement in Germany. In addition, however, vehicles that are actually affected are also excluded from the sticker requirement if they fulfil certain characteristics. In Germany, for example, these are all disabled vehicles with a blue EU parking permit and recognised classic cars with an H registration plate. It does not matter what type of vehicle it is. The fire brigade and police, as well as ambulances and the military, are also exempt from the sticker requirement.
In France, all motorbikes in vehicle category L also need a sticker. This leaves only tractors, which are generally exempt from the sticker requirement. Furthermore, vintage cars are not allowed in the low emission zones in France. Disabled vehicles do not need a sticker in Paris, just as in Germany. This is different in other French low emission zones. There, they always need a sticker, but as soon as it is affixed to the windscreen, the entry restrictions for disabled vehicles no longer apply. This means that disabled vehicles are then allowed to enter even if they only have a sticker, which is actually prohibited in a particular low emission zone. Public transport is also not affected by the sticker requirement in France. The French government has thus given its municipalities and cities the opportunity to continue to own (old) diesel buses, while other diesel vehicles are finding it increasingly difficult in France.
In Belgium, there are hardly any exceptions. Only the police, fire brigade and ambulances are exempt from the restrictions. In the Netherlands, on the other hand, there is a very long list of exemptions. In some cities there, these include removal vans, concrete mixers, circus wagons and show cars for fairs. The latter, however, require prior registration. Vintage cars are also exempt there, but only if they are over 40 years old. In Sweden, not only doctors are exempt from the rules of the environmental zones, but also nurses and midwives, even veterinarians, have free rides. The coast guard is also exempt from emission standards here. In the only Swiss low emission zone, in Geneva, taxis do not have to abide by the rules.
So in addition to the general rules, which sometimes only affect certain types of vehicles, there is an enormous variety of exemptions for the environmental zones. In the Green Zones app, you can add properties to your vehicle, such as "classic car" or "disabled vehicle", so that the app adjusts the map and the entry status of the environmental zones accordingly.
By the way, the most bizarre exceptions are probably in Italy. There, you are exempt from the rules in some municipalities if you are transporting pasta or flour. So the priorities are clearly defined there. Pasta comes before clean air.