A court will decide on Thursday whether German cities can ban heavily polluting cars, potentially wiping hundreds of millions of euros off the value of diesel cars on the country's roads. Environmental group DUH has sued Stuttgart in Germany's automaking heartland, and Duesseldorf over levels of particulate matter exceeding European Union limits after Volkswagen Group's 2015 admission to cheating diesel exhaust tests. The scandal led politicians across the world to scrutinize diesel emissions, which contain the matter and nitrogen oxide (NOx) and are known to cause respiratory disease. There are around 15 million diesel vehicles on German streets and environmental groups say levels of particulates exceed the EU threshold in at least 90 German towns and cities.