Several companies claim to have been developing compressed air cars for public use, since about 1990, but none are available yet. Typically the main advantages are claimed to be: no roadside emissions, low cost technology, engine uses food oil for lubrication, and integrated air conditioning. The tanks must be designed to safety standards appropriate for a pressure vessel, such as ISO 11439 . The storage tank may be made of: * carbon-fiber in order to reduce its weight while achieving the necessary strength. * kevlar.