Which vehicles are affected?
All vehicles are classified in one of emission categories 1 to 4. In Stuttgart the ban applies to all vehicles classified as belonging to Emission Category 1. As of July 1, 2010 the ban applies also to vehicles in Emission Category 2 and as of January 1, 2012 it applies also to vehicles in Emission Category 3.
According to the new vehicle classification regulations, vehicles with older US catalytic converters, which were previously classified as belonging to Emission Category 1, are now given an Emission Category 4 sticker, as are cars retrofitted with diesel soot filters in Euro-1 emission class and HGVs.