Local pollution and noise are essentially controlled on the basis of technical emission standards. These standards are continually being made more stringent, especially in the United States and the Scandinavian countries. For example, the United States is now promoting standards which will ultimately require vehicles to produce zero pollution(apart from carbon dioxide). Progress is slower as regards trucks. As far as noise is concerned, taxation seems to be effective for noise from aircraft; it can also be combined with regulations. Taxation produces revenues that can be used, for example, to soundproof dwellings, or to provide an incentive for the replacement of older, noisier aircraft.