Some of these programs also seek to improve the emission performance of diesel engines once in the hands of the end user.
Some state governments regulate diesel smoke emissions.
These standards established maximum allowable levels of emissions for regulated compounds from new engines. These standards have resulted in significant reductions in diesel engine emissions. Beginning in 2007, these new emission standards apply to heavy-duty highway engines and vehicles. By mid-2006, the level of sulfur in highway diesel fuel would have to be reduced by 97 percent from its current level of 500 parts per million to 15 parts per million. News and developments will be posted here as appropriate.