The International Council on Clean Transportation

Since the mid-1990s, developed countries have steadily tightened limits on heavy-duty vehicle emissions of NO_x, SO_x, carbon monoxide, particulates and other toxic pollutants. Developing countries have followed suit, usually modeling their standards on either US or European regulations. Similarly, regulators in most of the 10 largest motor vehicle markets have decreased the concentration of sulfur allowable in diesel and other fuels, both to reduce SO_x emissions and enable the use of pollution control technologies — such as diesel particulate filters and selective catalytic reduction — that require low-sulfur and ultra low-sulfur fuels. These charts show the progression of existing and proposed standards for toxic pollutants and diesel sulfur from 2005 to 2014 for the world's top 10 vehicle markets, plus Thailand.