Spilling All Sorts of Beans

Recently there has been a great fuss, across the United States, United Kingdom and the European Union, about the discovery that diesel cars can pollute more than was thought, and that some models were designed to work differently under test conditions as opposed to normal use, leading the authorities (and the car owners) to a false understanding of how polluting a given car was. The reaction to these discoveries, has been a movement to ban (or prohibitively tax) diesel cars from city centres, and politicians are now demanding a wholesale move to petrol engined cars. Before we do this, however, there needs to be a proper investigation into whether or not all the petrol engined models are actually any cleaner than the diesels. They are supposed to be, and when tested most petrol engined cars will appear to be clean, but that was also what was supposed to be true about the diesels. In the case of petrol engined cars, the comfortable assumptions about their low emissions needs to be chec