A few hours ahead of the expected decision of the Federal Administrative Court on driving bans for diesel cars in German cities, Greenpeace activists are demonstrating in Leipzig for clean air. In front of the courthouse, the environmentalists use chalk to paint a five-by-five-meter-long lung on the pavement. With a banner they demand: "Clean air is not negotiable." The court will probably decide soon whether cities that suffer from too much toxic nitrogen dioxide (NO2) can issue bans on diesel cars.